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Sample records for including attenuation due

  1. 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.

  2. Reverse attenuation in interaction terms due to covariate measurement error.

    PubMed

    Muff, Stefanie; Keller, Lukas F

    2015-11-01

    Covariate measurement error may cause biases in parameters of regression coefficients in generalized linear models. The influence of measurement error on interaction parameters has, however, only rarely been investigated in depth, and if so, attenuation effects were reported. In this paper, we show that also reverse attenuation of interaction effects may emerge, namely when heteroscedastic measurement error or sampling variances of a mismeasured covariate are present, which are not unrealistic scenarios in practice. Theoretical findings are illustrated with simulations. A Bayesian approach employing integrated nested Laplace approximations is suggested to model the heteroscedastic measurement error and covariate variances, and an application shows that the method is able to reveal approximately correct parameter estimates.

  3. Curcumin nanoparticles attenuate cardiac remodeling due to pulmonary arterial hypertension.

    PubMed

    Rice, Kevin M; Manne, Nandini D P K; Kolli, Madhukar B; Wehner, Paulette S; Dornon, Lucy; Arvapalli, Ravikumar; Selvaraj, Vellaisamy; Kumar, Arun; Blough, Eric R

    2016-12-01

    Herein, we investigate whether curcumin nanoparticles (Cur NPs) are effective for the treatment of monocrotaline (MCT)-induced pulmonary arterial hypertension in Sprague Dawley rat. Echocardiography was performed at the start of the study and 28 days after MCT injection. Compared to MCT only animals, Cur NP administration was associated with reduced right ventricular (RV) wall thickness and a decreased right ventricle weight/body weight ratio. Cur NPs also attenuated MCT induced increase in RV mRNA expression of TNF-α and IL-1β. These changes were also associated with decreased RV expression of nitrotyrosine, fibronectin and myosin heavy chain-β.

  4. 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.

  5. 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…

  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. 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…

  9. Bulk Attenuation in the Earth’s Mantle Due to Phase Transitions

    SciTech Connect

    L Li

    2011-12-31

    The calculated bulk attenuation due to phase transition from mineral physics data is reported here. With relaxation time less than 1 s, the calculated value for a pyrolite mantle is consistent with the inverted bulk attenuation of the upper mantle from seismic observations. The two important mechanisms of phase transitions, diffusion-controlled and kinetics-controlled, have different relaxation time as indicated by the models here. The diffusion controlled is more likely to contribute to the observed seismic bulk attenuation than the kinetic-controlled process based on the available diffusivity and kinetics data. The correlation between the bulk attenuation and relaxation time emphasizes the importance of a number of parameters in the mineral physics database such as Fe-Mg diffusivity and kinetics in olivine-wadsleyite-ringwoodite-perovskite, Mg-Ca-Al-Si diffusivity and kinetics in pyroxene-garnet-Ca perovskite, some of which are still unknown.

  10. The Correction for Attenuation Due to Measurement Error: Clarifying Concepts and Creating Confidence Sets

    ERIC Educational Resources Information Center

    Charles, Eric P.

    2005-01-01

    The correction for attenuation due to measurement error (CAME) has received many historical criticisms, most of which can be traced to the limited ability to use CAME inferentially. Past attempts to determine confidence intervals for CAME are summarized and their limitations discussed. The author suggests that inference requires confidence sets…

  11. The Correction for Attenuation Due to Measurement Error: Clarifying Concepts and Creating Confidence Sets

    ERIC Educational Resources Information Center

    Charles, Eric P.

    2005-01-01

    The correction for attenuation due to measurement error (CAME) has received many historical criticisms, most of which can be traced to the limited ability to use CAME inferentially. Past attempts to determine confidence intervals for CAME are summarized and their limitations discussed. The author suggests that inference requires confidence sets…

  12. Prediction of the outage performance of a microwave multiple-hop network due to rain attenuation

    NASA Astrophysics Data System (ADS)

    Kanellopoulos, John D.; Gakis, Lampros

    1987-10-01

    In the design of tandem links using frequencies above 10 GHz, it is necessary to estimate outage time occurrence probability due to rain attenuation. Subject of this paper is the theoretical analysis of simultaneous probability of rain attenuation for tendem links by studying the joint distribution of correlated lognormal variables. This analysis is appropriate to locations where the point rainrate distribution approximates the lognormal function. The theoretical predictions for the outage performance of the multiple-hop network have been compared with existing experimental data for tandem links located in France, USA and Japan. The agreement has been found to be encouraging.

  13. An energy-based approach to estimate seismic attenuation due to wave-induced fluid flow in heterogeneous poroelastic media

    NASA Astrophysics Data System (ADS)

    Solazzi, Santiago G.; Rubino, J. Germán; Müller, Tobias M.; Milani, Marco; Guarracino, Luis; Holliger, Klaus

    2016-11-01

    Wave-induced fluid flow (WIFF) due to the presence of mesoscopic heterogeneities is considered as one of the main seismic attenuation mechanisms in the shallower parts of the Earth's crust. For this reason, several models have been developed to quantify seismic attenuation in the presence of heterogeneities of varying complexity, ranging from periodically layered media to rocks containing fractures and highly irregular distributions of fluid patches. Most of these models are based on Biot's theory of poroelasticity and make use of the assumption that the upscaled counterpart of a heterogeneous poroelastic medium can be represented by a homogeneous viscoelastic solid. Under this dynamic-equivalent viscoelastic medium (DEVM) assumption, attenuation is quantified in terms of the ratio of the imaginary and real parts of a frequency-dependent, complex-valued viscoelastic modulus. Laboratory measurements on fluid-saturated rock samples also rely on this DEVM assumption when inferring attenuation from the phase shift between the applied stress and the resulting strain. However, whether it is correct to use an effective viscoelastic medium to represent the attenuation arising from WIFF at mesoscopic scales in heterogeneous poroelastic media remains largely unexplored. In this work, we present an alternative approach to estimate seismic attenuation due to WIFF. It is fully rooted in the framework of poroelasticity and is based on the quantification of the dissipated power and stored strain energy resulting from numerical oscillatory relaxation tests. We employ this methodology to compare different definitions of the inverse quality factor for a set of pertinent scenarios, including patchy saturation and fractured rocks. This numerical analysis allows us to verify the correctness of the DEVM assumption in the presence of different kinds of heterogeneities. The proposed methodology has the key advantage of providing the local contributions of energy dissipation to the overall

  14. A simple expression for sound attenuation due to surface duct energy leakage in low-latitude oceans.

    PubMed

    Duan, Rui; Yang, Kunde; Ma, Yuanliang; Chapman, N Ross

    2016-05-01

    This paper presents an expression for the attenuation of sound energy in an ocean surface duct due to energy leakage outside the duct. Dominant parameters determining the attenuation are the sound frequency and the surface duct thickness. The attenuation is found to be exponentially dependent on a scaled frequency that combines the two parameters. Data from experiments in low-latitude oceans with three different surface duct thicknesses are used to verify the exponential expression derived for the attenuation.

  15. 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. (For...

  16. 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. (For...

  17. 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.

  18. 25 CFR 42.7 - What does due process in a formal disciplinary proceeding include?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false What does due process in a formal disciplinary proceeding... RIGHTS § 42.7 What does due process in a formal disciplinary proceeding include? Due process must include... rendering a disciplinary decision. (b) The school must hold a fair and impartial hearing before imposing...

  19. Effective Medium Model for Ultrasonic Attenuation Due to the Thermo-Elastic Effect in Concentrated Emulsions

    NASA Astrophysics Data System (ADS)

    Hemar, Y.; Herrmann, N.; Lemaréchal, P.; Hocquart, R.; Lequeux, F.

    1997-04-01

    In this article, we deal with the propagation of ultrasonic waves in monodisperse concentrated oil in water emulsions. Using the approximation of Isakovich, we propose two different models, a mirror model and a core shell model, aiming to describe the temperature field in the dense medium and to supply a correct expression of the ultrasonic wave vector. The comparison between experimental data and theoretical models shows that the core shell model leads to a very accurate description of the ultrasonic attenuation, in a wide range of frequencies and concentrations, in the case where the thermo elastic effect, due to the scattering of thermal waves by the particles, is the dominant loss mechanism.

  20. Attenuation of the NMR signal in a field gradient due to stochastic dynamics with memory

    NASA Astrophysics Data System (ADS)

    Lisý, Vladimír; Tóthová, Jana

    2017-03-01

    The attenuation function S(t) for an ensemble of spins in a magnetic-field gradient is calculated by accumulation of the phase shifts in the rotating frame resulting from the displacements of spin-bearing particles. The found S(t), expressed through the particle mean square displacement, is applicable for any kind of stationary stochastic motion of spins, including their non-markovian dynamics with memory. The known expressions valid for normal and anomalous diffusion are obtained as special cases in the long time approximation. The method is also applicable to the NMR pulse sequences based on the refocusing principle. This is demonstrated by describing the Hahn spin echo experiment. The attenuation of the NMR signal is also evaluated providing that the random motion of particle is modeled by the generalized Langevin equation with the memory kernel exponentially decaying in time. The models considered in our paper assume massive particles driven by much smaller particles.

  1. Attenuation Characteristics of Strong Motions during the 2016 Kumamoto Earthquakes including Near-Field Records

    NASA Astrophysics Data System (ADS)

    Si, H.; Koketsu, K.; Miyake, H.; Ibrahim, R.

    2016-12-01

    During the two major earthquakes occurred in Kumamoto prefecture, at 21:26 on 14 April, 2016 (Mw 6.2, GCMT), and at 1:25 on 16 April, 2016 (Mw7.0, GCMT), a large number of strong ground motions were recorded, including those very close to the surface fault. In this study, we will discuss the attenuation characteristics of strong ground motions observed during the earthquakes. The data used in this study are mainly observed by K-NET, KiK-net, Osaka University, JMA and Kumamoto prefecture. The 5% damped acceleration response spectra (GMRotI50) are calculated based on the method proposed by Boore et al. (2006). PGA and PGV is defined as the larger one among the PGAs and PGVs of two horizontal components. The PGA, PGV, and GMRotI50 data were corrected to the bedrock with Vs of 1.5km/s based on the method proposed by Si et al. (2016) using the average shear wave velocity (Vs30) and the thickness of sediments over the bedrock. The thickness is estimated based on the velocity structure model provided by J-SHIS. We use a source model proposed by Koketsu et al. (2016) to calculate the fault distance and the median distance (MED) which defined as the closest distance from a station to the median line of the fault plane (Si et al., 2014). We compared the observed PGAs, PGVs, and GMRotI50 with the GMPEs developed in Japan using MED (Si et al., 2014). The predictions by the GMPEs are generally consistent with the observations during the two Kumamoto earthquakes. The results of the comparison also indicated that, (1) strong motion records from the earthquake on April 14th are generally consistent with the predictions by GMPE, however, at the periods of 0.5 to 2 seconds, several records close to the fault plane show larger amplitudes than the predictions by GMPE, including the KiK-net station Mashiki (KMMH16); (2) for the earthquake on April 16, the PGAs and GMRotI50 at periods from 0.1s to 0.4s with short distance from the fault plane are slightly smaller than the predictions by

  2. Quantifying Wave Attenuation due to Salt Marshes with a Phase-Averaged Wave Model

    NASA Astrophysics Data System (ADS)

    Marsooli, R.; Orton, P. M.; Blumberg, A. F.; Georgas, N.

    2016-12-01

    This study uses a mixture of laboratory validation, real-world site/scenario modeling, and data on seasonal variation in salt marsh characteristics to quantify their capacity to mitigate storm waves. We assess the accuracy of four existing empirical formulas to determine the vegetation drag coefficient and, in turn, vegetation-induced wave attenuation. We adopt these formulas in the phase-averaged wave model of Mellor et al. (2008), MDO hereafter, which is improved in the present study to simulate wave energy dissipation due to vegetation drag force. One attribute of MDO is speed, due to parameterized energy in frequency space, and as a result the model may be preferable for hazard assessments and ensemble forecasting. We evaluate the performance of the improved MDO wave model and the empirical drag formulas using existing laboratory data. Comparisons between the model results and measurements show that the model based on the drag formula of Kobayashi et al. (1993) performs better than other models. We further apply MDO based on this formula to Jamaica Bay, the largest natural open space left in New York City, to quantify the influence of estuarine-scale salt marshes on storm waves. The model results show that the vegetation in summer season, when Spartina alterniflora is at its maximum height, is more effective to reduce wave height than in fall season. Moreover, the influence of the Spartina on wave height is more pronounced during a severe storm than a moderate storm. This is because the smaller water depth during a moderate storm causes intense depth-induced wave breaking over shallow marsh islands and thus the contribution of vegetation drag to wave attenuation becomes negligible. On the other hand, during a severe storm with high water elevation, the depth-induced breaking is small and vegetation-induced drag becomes the primary source of wave attenuation.

  3. Natural attenuation of Fukushima-derived radiocesium in soils due to its vertical and lateral migration.

    PubMed

    Konoplev, A; Golosov, V; Wakiyama, Y; Takase, T; Yoschenko, V; Yoshihara, T; Parenyuk, O; Cresswell, A; Ivanov, M; Carradine, M; Nanba, K; Onda, Y

    2017-08-28

    Processes of vertical and lateral migration lead to gradual reduction in contamination of catchment soil, particularly its top layer. The reduction can be considered as natural attenuation. This, in turn, results in a gradual decrease of radiocesium activity concentrations in the surface runoff and river water, in both dissolved and particulate forms. The purpose of this research is to study the dynamics of Fukushima-derived radiocesium in undisturbed soils and floodplain deposits exposed to erosion and sedimentation during floods. Combined observations of radiocesium vertical distribution in soil and sediment deposition on artificial lawn-grass mats on the Niida River floodplain allowed us to estimate both annual mean sediment accumulation rates and maximum sedimentation rates corresponding to an extreme flood event during Tropical Storm Etau, 6-11 September 2015. Dose rates were reduced considerably for floodplain sections with high sedimentation because the top soil layer with high radionuclide contamination was eroded and/or buried under cleaner fresh sediments produced mostly due to bank erosion and sediments movements. Rate constants of natural attenuation on the sites of the Takase River and floodplain of Niida River was found to be in range 0.2-0.4 year(-1). For the site in the lower reach of the Niida River, collimated shield dose readings from soil surfaces slightly increased during the period of observation from February to July 2016. Generally, due to more precipitation, steeper slopes, higher temperatures and increased biological activities in soils, self-purification of radioactive contamination in Fukushima associated with vertical and lateral radionuclide migration is faster than in Chernobyl. In many cases, monitored natural attenuation along with appropriate restrictions seems to be optimal option for water remediation in Fukushima contaminated areas. Copyright © 2017. Published by Elsevier Ltd.

  4. An Expanded UV Irradiance Database from TOMS Including the Effects of Ozone, Clouds, and Aerosol Attenuation

    NASA Technical Reports Server (NTRS)

    Herman, J.; Krotkov, N.

    2003-01-01

    The TOMS UV irradiance database (1978 to 2003) has been expanded to include five new products (noon irradiance at 305,310,324, and 380 nm, and noon erythemal-weighted irradiance), in addition to the existing erythemal daily exposure, that permit direct comparisons with ground-based measurements from spectrometers and broadband instruments. The new data are available on http://toms.gsfc.nasa.gov/>http://toms.gsfc.nasa.gov. Comparisons of the TOMS estimated irradiances with ground-based instruments are given along with a review of the sources of known errors, especially the recent improvements in accounting for aerosol attenuation. Trend estimations from the new TOMS irradiances permit the clear separation of changes caused by ozone and those caused by aerosols and clouds. Systematic differences in cloud cover are shown to be the most important factor in determining regional differences in UV radiation reaching the ground for locations at the same latitude (e.g., the summertime differences between Australia and the US southwest).

  5. 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

  6. False-positive pericardial effusion due to breast attenuation on equilibrium radionuclide angiocardiography.

    PubMed

    Mar, Martha V; Kim, E Edmund

    2011-06-01

    Equilibrium radionuclide angiocardiography (ERNA) scans are used to evaluate left ventricular function and pericardial anatomy. A photopenic "U-halo" around the cardiac blood pool in the left anterior oblique (LAO) view is commonly seen with pericardial effusion. We describe findings of false-positive pericardial effusion due to breast attenuation in cancer patients. Several cases that demonstrated the photopenic U-halo in the LAO view did not have true pericardial effusion. The patients' breast size and how far the breast sagged in reference to the heart silhouette were visually observed in topograms. The oblique tilt position was evaluated to determine the effect it may have in creating the photopenic U-halo. A unique ERNA case demonstrating collateral vessels bilaterally in the breasts was used as a reference marker image to determine the effect of a slightly more anterior versus left lateral oblique tilt in the LAO view. Large breasts can overlie the heart in the LAO projection. The overlying breast can cause the appearance of pericardial effusion in the resulting image by attenuating tissues surrounding the heart. The positioning of the breast also affected the appearance of the photopenic halo. A patient with breast implants who had more upright breasts demonstrated a photopenic area anterior to the left ventricle, whereas a large breast that sagged more laterally demonstrated no photopenic area. Patients with large breasts may show a photopenic U-halo in the LAO view dependent on how far the breast sags in reference to the heart silhouette and on the positioning of the oblique tilt. The anterior image should be used to distinguish breast attenuation from a photopenic area surrounding the heart. If both the anterior view and the LAO view demonstrate the U-halo, acquiring another view with a slightly more anterior or lateral oblique position will demonstrate any inconsistency in the photopenic area, thereby excluding a diagnosis of pericardial effusion.

  7. The Attenuated Genotype of Varicella-Zoster Virus Includes an ORF0 Transitional Stop Codon Mutation

    PubMed Central

    Peters, Geoffrey A.; Tyler, Shaun D.; Carpenter, John E.; Jackson, Wallen; Mori, Yasuko; Arvin, Ann M.

    2012-01-01

    Varicella-zoster virus (VZV) is the first of the human herpesviruses to be attenuated and subsequently approved as a live vaccine to prevent varicella and herpes zoster. Both the attenuated VZV vaccine, called vaccine Oka or vOka, and the parental strain pOka have been completely sequenced. Yet the specific determinants of attenuation are uncertain. The open reading frame (ORF) with the most single nucleotide polymorphisms (SNPs), ORF62, encodes the regulatory protein IE62, but IE62 studies have failed to define a specific SNP associated with attenuation. We have completed next-generation sequencing of the VZV Ellen genome, a strain known to be highly attenuated by its very limited replication in human skin xenografts in the SCID mouse model of VZV pathogenesis. A comparative analysis of the Ellen sequence with all other complete VZV sequences was extremely informative. In particular, an unexpected finding was a stop codon mutation in Ellen ORF0 (herpes simplex virus UL56 homolog) identical to one found in vOka, combined with the absence of polymorphisms in most Ellen ORFs that were known to be mutated in vOka. The mutated ORF0 protein was also imaged in both two dimensions and three dimensions by confocal microscopy. The probability of two VZV strains not connected by a recent common ancestor having an identical ORF0 SNP by chance would be 1 × 10−8, in other words, extremely unlikely. Taken together, these bioinformatics analyses strongly suggest that the stop codon ORF0 SNP is one of the determinants of the attenuation genotype of live VZV vaccines. PMID:22837206

  8. 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.

  9. 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.

  10. 25 CFR 162.417 - What requirements for due diligence must a business lease include?

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 25 Indians 1 2014-04-01 2014-04-01 false What requirements for due diligence must a business lease... WATER LEASES AND PERMITS Business Leases Lease Requirements § 162.417 What requirements for due diligence must a business lease include? (a) If permanent improvements are to be constructed, the...

  11. 20 CFR 410.410 - Total disability due to pneumoconiosis, including statutory presumption.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... FEDERAL COAL MINE HEALTH AND SAFETY ACT OF 1969, TITLE IV-BLACK LUNG BENEFITS (1969- ) Total Disability or Death Due to Pneumoconiosis § 410.410 Total disability due to pneumoconiosis, including statutory... their death. (For benefits to the eligible survivors of miners whose deaths are determined to have...

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

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 25 Indians 1 2013-04-01 2013-04-01 false What requirements for due diligence must a WEEL include? 162.517 Section 162.517 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR LAND AND WATER LEASES AND PERMITS Wind and Solar Resource Leases Weels § 162.517 What requirements for due...

  13. Results of the VPI&SU Comstar experiment. [depolarization and attenuation due to rain

    NASA Technical Reports Server (NTRS)

    Andrews, J. H.; Ozbay, C.; Pratt, T.; Bostian, C. W.; Manus, E. A.; Gaines, J. M.; Marshall, R. E.; Stutzman, W. L.; Wiley, P. H.

    1982-01-01

    This paper summarizes annual and cumulative attenuation data, depolarization data, and associated local rain rate distributions obtained with the Comstar family of 19.04- and 28.56-GHz satellite beacons during the years 1977-1981. It discusses the relationships between attenuation and rain rate and between attenuation and depolarization, compares measured data on the joint distribution of attenuation and depolarization, and examines the limitations that propagation effects will impose on future 20/30-GHz satellite communications systems.

  14. Simulation of stress waves in attenuating drill strings, including piezoelectric sources and sensors

    PubMed

    Carcione; Poletto

    2000-07-01

    A key element in drill steering and prediction of lithology ahead-of-the-bit is the transmission of while-drilling information from the bottom of the well to the rig operator and the geophysicists. Mud-pulse telemetry, based on pressure pulses along the drilling mud and extensional waves through the drill string, is the most used technique. The last method, properly designed, could transmit data rates up to 100 bits per second, against the 1 or 2 bits per second achieved with pressure pulses. In this work, a time-domain algorithm is developed for the propagation of one-dimensional axial, torsional, and flexural stress waves, including transducer sources and sensors. In addition, the equations include relaxation mechanisms simulating the viscoelastic behavior of the steel, dielectric losses, and any other losses, such as those produced by the presence of the drilling mud, the casing, and the formation. Moreover, the algorithm simulates the passbands and stopbands due to the presence of the coupling joints and pulse distortion and delay due to nonuniform cross-section areas. Acoustic and electric pulses, generated at one location in the string, can be propagated and detected at any other location by piezoelectric and acoustic sensors, such as PCB accelerometers, clamp-on ammeters, force, and strain transducers.

  15. 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.

  16. FUNDAMENTAL AREAS OF PHENOMENOLOGY (INCLUDING APPLICATIONS): Ultrasound Attenuation in Biological Tissue Predicted by the Modified Doublet Mechanics Model

    NASA Astrophysics Data System (ADS)

    Jiang, Xin; Liu, Xiao-Zhou; Wu, Jun-Ru

    2009-07-01

    Experimental results have shown that in the megahertz frequency range the relationship between the acoustic attenuation coefficient in soft tissues and frequency is nearly linear. The classical continuum mechanics (CCM), which assumes that the material is uniform and continuous, fails to explain this relationship particularly in the high megahertz range. Doublet mechanics (DM) is a new elastic theory which takes the discrete nature of material into account. The current DM theory however does not consider the loss. We revise the doublet mechanics (DM) theory by including the loss term, and calculate the attenuation of a soft tissue as a function of frequency using the modified the DM theory (MDM). The MDM can now well explain the nearly linear relationship between the acoustic attenuation coefficient in soft tissues and frequency.

  17. High-resolution gamma ray attenuation density measurements on mining exploration drill cores, including cut cores

    NASA Astrophysics Data System (ADS)

    Ross, P.-S.; Bourke, A.

    2017-01-01

    Physical property measurements are increasingly important in mining exploration. For density determinations on rocks, one method applicable on exploration drill cores relies on gamma ray attenuation. This non-destructive method is ideal because each measurement takes only 10 s, making it suitable for high-resolution logging. However calibration has been problematic. In this paper we present new empirical, site-specific correction equations for whole NQ and BQ cores. The corrections force back the gamma densities to the "true" values established by the immersion method. For the NQ core caliber, the density range extends to high values (massive pyrite, 5 g/cm3) and the correction is thought to be very robust. We also present additional empirical correction factors for cut cores which take into account the missing material. These "cut core correction factors", which are not site-specific, were established by making gamma density measurements on truncated aluminum cylinders of various residual thicknesses. Finally we show two examples of application for the Abitibi Greenstone Belt in Canada. The gamma ray attenuation measurement system is part of a multi-sensor core logger which also determines magnetic susceptibility, geochemistry and mineralogy on rock cores, and performs line-scan imaging.

  18. 25 CFR 162.546 - What requirements for due diligence must a WSR lease include?

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 25 Indians 1 2013-04-01 2013-04-01 false What requirements for due diligence must a WSR lease include? 162.546 Section 162.546 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR LAND AND WATER LEASES AND PERMITS Wind and Solar Resource Leases Wsr Leases § 162.546 What requirements for...

  19. 25 CFR 42.7 - What does due process in a formal disciplinary proceeding include?

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... disciplinary action, except under the following circumstances: (1) If the Act requires immediate removal (such... 25 Indians 1 2011-04-01 2011-04-01 false What does due process in a formal disciplinary proceeding include? 42.7 Section 42.7 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR EDUCATION...

  20. 25 CFR 42.7 - What does due process in a formal disciplinary proceeding include?

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... disciplinary action, except under the following circumstances: (1) If the Act requires immediate removal (such... 25 Indians 1 2014-04-01 2014-04-01 false What does due process in a formal disciplinary proceeding include? 42.7 Section 42.7 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR EDUCATION...

  1. 25 CFR 42.7 - What does due process in a formal disciplinary proceeding include?

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... disciplinary action, except under the following circumstances: (1) If the Act requires immediate removal (such... 25 Indians 1 2013-04-01 2013-04-01 false What does due process in a formal disciplinary proceeding include? 42.7 Section 42.7 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR EDUCATION...

  2. 25 CFR 42.7 - What does due process in a formal disciplinary proceeding include?

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... disciplinary action, except under the following circumstances: (1) If the Act requires immediate removal (such... 25 Indians 1 2012-04-01 2011-04-01 true What does due process in a formal disciplinary proceeding include? 42.7 Section 42.7 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR EDUCATION...

  3. Spectral solar attenuation due to aerosol loading over an urban area in India

    NASA Astrophysics Data System (ADS)

    Latha, K. Madhavi; Badarinath, K. V. S.

    2005-06-01

    Anthropogenic activities in urban areas are sources for atmospheric aerosols and are increasing due to population explosion and migration. Many large cities in the developing world are presently plagued by high levels of atmospheric pollution and long-term effect of urban aerosol on climate is an important topic. In the present study, ground-based measurements of solar irradiance, aerosol loading and black carbon (BC) aerosol concentration have been analyzed during different aerosol loading conditions during 2003 over an urban environment. BC aerosols concentration has been observed to be enhanced during high aerosol optical depth day suggesting influence of local anthropogenic activities. The analysis of wind fields over the study area during the measurement period is from north with continental air mass prevailing over the region. Spectral measurements of solar irradiance exhibited variations based on aerosol loading in urban atmosphere. Relative attenuations caused by aerosols have been found to be of the order of 21% and 17% on the irradiance on visible and near infrared respectively.

  4. Microwave Propagation Attenuation due to Earth's Atmosphere and Weather at SHF Band

    NASA Technical Reports Server (NTRS)

    Ho, Christian; Wang, Charles; Gritton, Kelly; Angkasa, Kris

    2004-01-01

    In this study we have estimated radio wave propagation losses at super high frequency (SHF) band by applying available propagation models into several Air Force benchmark scenarios. The study shows that dominantly additional losses over the free space loss are atmospheric absorption, clouds, fog, and precipitation, as well as scintillation /multipath at low elevation angles. The free space loss equation has been modified to include all atmospheric attenuation and fading effects that cannot be neglected over the range of frequency of interest. Terrain profiles along all directions of interest within the coastal areas and inland areas for four benchmark cases have been analyzed in detail. We find that while the atmospheric gaseous absorption plays a significant role under a clear weather, heavy rainfalls can cause several tens of dB loss for a 100- km path through the rain. At very low elevation angles (< 5 deg), atmospheric scintillation/multipath fading becomes a very important factor. There are significant differences in the feature of anomalous mode (ducting) propagation between the east and the west coastal receiving stations.

  5. Microwave Propagation Attenuation due to Earth's Atmosphere and Weather at SHF Band

    NASA Technical Reports Server (NTRS)

    Ho, Christian; Wang, Charles; Gritton, Kelly; Angkasa, Kris

    2004-01-01

    In this study we have estimated radio wave propagation losses at super high frequency (SHF) band by applying available propagation models into several Air Force benchmark scenarios. The study shows that dominantly additional losses over the free space loss are atmospheric absorption, clouds, fog, and precipitation, as well as scintillation /multipath at low elevation angles. The free space loss equation has been modified to include all atmospheric attenuation and fading effects that cannot be neglected over the range of frequency of interest. Terrain profiles along all directions of interest within the coastal areas and inland areas for four benchmark cases have been analyzed in detail. We find that while the atmospheric gaseous absorption plays a significant role under a clear weather, heavy rainfalls can cause several tens of dB loss for a 100- km path through the rain. At very low elevation angles (< 5 deg), atmospheric scintillation/multipath fading becomes a very important factor. There are significant differences in the feature of anomalous mode (ducting) propagation between the east and the west coastal receiving stations.

  6. Electromagnetic wave attenuation due to the charged particles in dust&sand (DUSA) storms

    NASA Astrophysics Data System (ADS)

    Dou, X. Q.; Xie, L.

    2017-07-01

    In this paper, we calculated the attenuation of the electromagnetic waves (EMWs) propagating through the dust&sand (DUSA) storms using the predicting model based on Mie theory, in which the charges carried on the DUSA particles, the ambient relative humidity (RH) and the particle size distribution are considered simultaneously. It can be found that the charges carried on the DUSA particles and the RH can change the value of the absorption and scattering efficiency, but they can't change the domain attenuation mechanism caused by the DUSA storms in the EMWs frequency regions (3 GHz, 4 GHz), (8 GHz, 40 GHz) and (75 GHz, 100 GHz). Whatever the DUSA storms are formed by equal-size particles or the mixed-size particles, the charge carried on the particle surface and the RH have a significant impact on the attenuation caused by the DUSA storms, and the change ratio of the attenuation caused by the charge or RH depends on the particle size. By the comparison of the calculated attenuation with the measured one, we found that the charges carried on the particles and the RH will be important factors to affect the attenuation of the EMWs.

  7. 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.

  8. Investigating treatment dose error due to beam attenuation by a carbon fiber tabletop.

    PubMed

    Myint, W Kenji; Niedbala, Malgorzata; Wilkins, David; Gerig, Lee H

    2006-08-24

    Carbon fiber is commonly used in radiation therapy for treatment tabletops and various immobilization and support devices, partially because it is generally perceived to be almost radiotransparent to high-energy photons. To avoid exposure to normal tissue during modern radiation therapy, one must deliver the radiation from all gantry angles; hence, beams often transit the couch proximal to the patient. The effects of the beam attenuation by the support structure of the couch are often neglected in the planning process. In this study, we investigate the attenuation of 6-MV and 18-MV photon beams by a Medtec (Orange City, IA) carbon fiber couch. We have determined that neglecting the attenuation of oblique treatment fields by the carbon fiber couch can result in localized dose reduction from 4% to 16%, depending on energy, field size, and geometry. Further, we investigate the ability of a commercial treatment-planning system (Theraplan Plus v3.8) to account for the attenuation by the treatment couch. Results show that incorporating the carbon fiber couch in the patient model reduces the dose error to less than 2%. The variation in dose reduction as a function of longitudinal couch position was also measured. In the triangular strut region of the couch, the attenuation varied +/- 0.5% following the periodic nature of the support structure. Based on these findings, we propose the routine incorporation of the treatment tabletop into patient treatment planning dose calculations.

  9. 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.

  10. Centimeter and millimeter wave attenuation and brightness temperature due to atmospheric oxygen and water vapor

    NASA Technical Reports Server (NTRS)

    Smith, E. K.

    1982-01-01

    Calculations are presented for atmospheric absorption and radiation emission for several atmospheric conditions and elevation angles. The calculations are for frequencies in the 1 to 340 GHz frequency range. The calculations are compared to those from other models. Agreement is found to within 15% for absorption coefficient (7.5 g/m/cubed water vapor at 290 K) and approximately the same for total zenithal attenuation. The attenuation and gaseous emission noise curves defined by the International Radio Consultative Committee are found to have minor inconsistencies.

  11. 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.

  12. Noise Attenuation Loss Due to Wearing APEL Eye Protection with Ear-Muff Style Headset Systems

    DTIC Science & Technology

    2012-02-14

    have active noise reduction (ANR) circuitry which attenuates low frequency sounds by electronically generating an equal but opposite pressure wave...insertion loss) provided by each combination. 4 Equipment The test procedure utilized a binaural KEMAR manikin, two QSC Audio PLX 3402 power...control circuit modules (PXle-8360, PXI-6620, PXI-4461), and a personal computer running Windows XP. The sound field was generated using REATMaster

  13. Hybrid wireless underground sensor networks - Quantification of signal attenuation due to soil adsorption

    NASA Astrophysics Data System (ADS)

    Huisman, J. A.; Bogena, H. R.; Meier, H.; Weuthen, A.; Rosenbaum, U.; Vereecken, H.

    2008-12-01

    A promising new technology for environmental monitoring is the wireless sensor network. Recently, we developed a sensor network for the near real-time monitoring of soil moisture. This network is based on the new low-cost ZigBee radio network that operates on top of the IEEE 802.15.4 standard. The sensor network consists of soil moisture sensors attached to end devices by cables, router devices and a coordinator device. The end devices are buried in the soil and linked wirelessly with nearby aboveground router devices (i.e. it is a hybrid wireless sensor network). A key concern with these hybrid networks is the quality of the wireless link through the soil. In this study, we measured and modelled the signal attenuation of a 5 cm soil layer. We developed a laboratory experimental setup to measure signal attenuation for a range of soil water contents and bulk electrical conductivities. These data were then used to validate a semi-empirical electromagnetic model simulating signal attenuation. The validated model was then used to show how wireless sensor transmitter range is affected by soil adsorption for different soil conditions.

  14. 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

  15. 20 CFR 410.410 - Total disability due to pneumoconiosis, including statutory presumption.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... presumption. (a) Benefits are provided under the Act to coal miners “who are totally disabled due to... establish: (1) That he is a coal miner, that he is totally disabled due to pneumoconiosis, and that his... FEDERAL COAL MINE HEALTH AND SAFETY ACT OF 1969, TITLE IV-BLACK LUNG BENEFITS (1969- ) Total Disability or...

  16. 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.

  17. 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 the...

  18. 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 resource...

  19. [Ciprofloxacin and therapy of urinary tract infections, including those due to Staphylococcus saprophyticus].

    PubMed

    Ivanov, D V; Budanov, S V

    2006-01-01

    Staphylococcus saprophyticus is one of the main pathogens of cystitis in young women. The human biotopes are contaminated by the staphylococcus on direct contacts with domestic animals or after using not properly cooked food of animal origin. Young women are more susceptible to colonization of the urinary tract by S. saprophyticus vs. the other contingents. Sexual intercourse is conducive to the colonization and infection. Shifts in the urinary tract microflora due to the use of spermicide, as well as candidiasis promote colonization of the urinary tract by S. saprophyticus. At present fluoroquinolones are considered as a significant independent group of chemotherapeutics within the class of quinolones, inhibitors of DNA gyrase, characterized by high clinical efficacy in the treatment of urinary tract infections. Especially significant clinical experience with ciprofloxacin in the therapy of urinary tract infections is available.

  20. 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

  1. Role of vegetation on the attenuation of forces on structures due to cnoidal waves

    NASA Astrophysics Data System (ADS)

    2009-04-01

    The evaluation of forces on structures in the marine environment due to ocean waves is absolutely essential in the planning and development of mitigation measures against natural coastal hazards and dictates their design. Further, studies on the forces on coastal structures due to regular and random waves are well entrenched in literature, whereas, that due to shallow water waves are rather scanty. The recent tsunami has added a new dimension on the role of vegetation on the forces on structures. Due the propagation of tsunami, a number of signature studies have revealed that structures fronted by vegetation have suffered minimum damage compared to that in its absence and as also reported by Yanagisawa (2008). In the present paper, the results from an experimental study to investigate the effect of vegetation on a typical structure located onshore over a slope of 1:30 are reported. The tests were carried out in a wave flume of length 72m, width 2m and 2.7m depth. The water depth at the toe of the slope was 1m. Slender flexible cylindrical members that represent plantation along the coast have been adopted for the tests. Experiments were carried out for different G/B ratios of 0, 0.5,1 and 1.5. (Where G is the distance between front face of vegetation/ green belt and the rear face of the building and B is width of the building). Experiments were repeated for three widths of Green belts (BG) and for each of the green belt, two different diameters of the cylinders of 10mm and 3.0mm were used. The forces on structure were measured with load cells in the presence and absence of the green belt. The Cnoidal waves covering a range of Ursell parameter between 18 and 700 were employed for the experiments. The different vegetal and flow parameters in a non-dimensional form have been identified. The variation of non-dimensionalised force over the slope in the presence and absence of vegetation as a function of the Ursell parameter, Relative rigidity and Reduced velocity for

  2. Role of vegetation on the attenuation of forces on structures due to Cnoidal waves

    NASA Astrophysics Data System (ADS)

    Sundar, V.; Norayanan, L.; Murali, K.

    2009-04-01

    The evaluation of forces on structures in the marine environment due to ocean waves is absolutely essential in the planning and development of mitigation measures against natural coastal hazards and dictates their design. Further, studies on the forces on coastal structures due to regular and random waves are well entrenched in literature, whereas, that due to shallow water waves are rather scanty. The recent tsunami has added a new dimension on the role of vegetation on the forces on structures. Due the propagation of tsunami, a number of signature studies have revealed that structures fronted by vegetation have suffered minimum damage compared to that in its absence and as also reported by Yanagisawa (2008). In the present paper, the results from an experimental study to investigate the effect of vegetation on a typical structure located onshore over a slope of 1:30 are reported. The tests were carried out in a wave flume of length 72m, width 2m and 2.7m depth. The water depth at the toe of the slope was 1m. Slender flexible cylindrical members that represent plantation along the coast have been adopted for the tests. Experiments were carried out for different G/B ratios of 0, 0.5,1 and 1.5. (Where G is the distance between front face of vegetation/ green belt and the rear face of the building and B is width of the building). Experiments were repeated for three widths of Green belts (BG) and for each of the green belt, two different diameters of the cylinders of 10mm and 3.0mm were used. The forces on structure were measured with load cells in the presence and absence of the green belt. The Cnoidal waves covering a range of Ursell parameter between 18 and 700 were employed for the experiments. The different vegetal and flow parameters in a non-dimensional form have been identified. The variation of non-dimensionalised force over the slope in the presence and absence of vegetation as a function of the Ursell parameter, Relative rigidity and Reduced velocity for

  3. Glucosamines Attenuate Bone Loss Due to Menopause by Regulating Osteoclast Function in Ovariectomized Mice.

    PubMed

    Asai, Hironobu; Nakatani, Sachie; Kato, Takuya; Shimizu, Tatsuo; Mano, Hiroshi; Kobata, Kenji; Wada, Masahiro

    2016-01-01

    The effect of glucosamine (GlcN) and N-acetylglucosamine (GlcNAc) on bone metabolism in ovariectomized (OVX) mice was studied. After 12 weeks of feeding with 0.2% GlcN and 0.2% GlcNAc, the femoral bone mineral density in OVX mice was significantly increased compared with that in OVX mice fed the control diet. Histomorphometric analysis of the tibia indicated that the rates of osteogenesis and bone resorption were reduced due to the GlcN diet. The erosion depth of osteoclasts on the tibia in GlcN- and GlcNAc-fed OVX mice was significantly lower than that in the control OVX mice. The number of tartrate-resistant acid phosphatase-positive osteoclasts induced from bone marrow stem cells isolated from GlcN-fed OVX mice was significantly lower than that from control OVX mice. A loss of uterine weight and higher serum calcium concentration in the GlcN- and GlcNAc-fed OVX mice were observed. The results suggest that the intake of GlcN suppresses bone loss by inhibiting osteoclast differentiation and activity in a nonestrogenic manner.

  4. Evaluation of the vibration attenuation properties of an air-inflated cushion with two different heavy machinery seats in multi-axis vibration environments including jolts.

    PubMed

    Ji, Xiaoxu; Eger, Tammy R; Dickey, James P

    2017-03-01

    Seats and cushions can attenuate whole-body vibration (WBV) exposures and minimize health risks for heavy machine operators. We successfully developed neural network (NN) algorithms to identify the vibration attenuation properties for four different seating conditions (seat/cushion combinations), and implemented each of the NN models to predict the equivalent daily exposure A(8) values for various vehicles in the forestry and mining environments. We also evaluated the performance of the new prototype No-Jolt™ air-inflated cushion and the original cushion of each seat with jolt exposures. We observed that the air cushion significantly improved the vibration attenuation properties of the seat that initially had good performance, but not for the seat that had relatively poor vibration attenuation properties. In addition, operator's anthropometrics and sex influenced the performance of the air-inflated cushion when the vibration environment included jolt exposures.

  5. A (p)ppGpp-Null Mutant of Haemophilus ducreyi Is Partially Attenuated in Humans Due to Multiple Conflicting Phenotypes

    PubMed Central

    Holley, Concerta; Gangaiah, Dharanesh; Li, Wei; Fortney, Kate R.; Janowicz, Diane M.; Ellinger, Sheila; Zwickl, Beth; Katz, Barry P.

    2014-01-01

    (p)ppGpp responds to nutrient limitation through a global change in gene regulation patterns to increase survival. The stringent response has been implicated in the virulence of several pathogenic bacterial species. Haemophilus ducreyi, the causative agent of chancroid, has homologs of both relA and spoT, which primarily synthesize and hydrolyze (p)ppGpp in Escherichia coli. We constructed relA and relA spoT deletion mutants to assess the contribution of (p)ppGpp to H. ducreyi pathogenesis. Both the relA single mutant and the relA spoT double mutant failed to synthesize (p)ppGpp, suggesting that relA is the primary synthetase of (p)ppGpp in H. ducreyi. Compared to the parent strain, the double mutant was partially attenuated for pustule formation in human volunteers. The double mutant had several phenotypes that favored attenuation, including increased sensitivity to oxidative stress. The increased sensitivity to oxidative stress could be complemented in trans. However, the double mutant also exhibited phenotypes that favored virulence. When grown to the mid-log phase, the double mutant was significantly more resistant than its parent to being taken up by human macrophages and exhibited increased transcription of lspB, which is involved in resistance to phagocytosis. Additionally, compared to the parent, the double mutant also exhibited prolonged survival in the stationary phase. In E. coli, overexpression of DksA compensates for the loss of (p)ppGpp; the H. ducreyi double mutant expressed higher transcript levels of dksA than the parent strain. These data suggest that the partial attenuation of the double mutant is likely the net result of multiple conflicting phenotypes. PMID:24914217

  6. A (p)ppGpp-null mutant of Haemophilus ducreyi is partially attenuated in humans due to multiple conflicting phenotypes.

    PubMed

    Holley, Concerta; Gangaiah, Dharanesh; Li, Wei; Fortney, Kate R; Janowicz, Diane M; Ellinger, Sheila; Zwickl, Beth; Katz, Barry P; Spinola, Stanley M

    2014-08-01

    (p)ppGpp responds to nutrient limitation through a global change in gene regulation patterns to increase survival. The stringent response has been implicated in the virulence of several pathogenic bacterial species. Haemophilus ducreyi, the causative agent of chancroid, has homologs of both relA and spoT, which primarily synthesize and hydrolyze (p)ppGpp in Escherichia coli. We constructed relA and relA spoT deletion mutants to assess the contribution of (p)ppGpp to H. ducreyi pathogenesis. Both the relA single mutant and the relA spoT double mutant failed to synthesize (p)ppGpp, suggesting that relA is the primary synthetase of (p)ppGpp in H. ducreyi. Compared to the parent strain, the double mutant was partially attenuated for pustule formation in human volunteers. The double mutant had several phenotypes that favored attenuation, including increased sensitivity to oxidative stress. The increased sensitivity to oxidative stress could be complemented in trans. However, the double mutant also exhibited phenotypes that favored virulence. When grown to the mid-log phase, the double mutant was significantly more resistant than its parent to being taken up by human macrophages and exhibited increased transcription of lspB, which is involved in resistance to phagocytosis. Additionally, compared to the parent, the double mutant also exhibited prolonged survival in the stationary phase. In E. coli, overexpression of DksA compensates for the loss of (p)ppGpp; the H. ducreyi double mutant expressed higher transcript levels of dksA than the parent strain. These data suggest that the partial attenuation of the double mutant is likely the net result of multiple conflicting phenotypes.

  7. 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

  8. 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.

  9. New analytical approach to calibrate the co-axial HPGe detectors including correction for source matrix self-attenuation.

    PubMed

    Badawi, Mohamed S; Gouda, Mona M; Nafee, Sherif S; El-Khatib, Ahmed M; El-Mallah, Ekram A

    2012-12-01

    To calibrate the co-axial HPGe semiconductor detectors, we introduce a new theoretical approach based on the Direct Statistical method proposed by Selim and Abbas (1995, 1996) to calculate the full-energy peak efficiency for cylindrical detectors. The present method depends on the accurate analytical calculation of the average path length covered by the photon inside the detector active volume and the geometrical solid angle Ω, to obtain a simple formula for the efficiency. In addition, the self attenuation coefficient of the source matrix (with a radius greater than the detector's radius), the attenuation factors of the source container and the detector housing materials are also treated by calculating the average path length within these materials. (152)Eu aqueous radioactive sources covering the energy range from 121 to 1408 keV were used. Remarkable agreement between the measured and the calculated efficiencies was achieved with discrepancies less than 2%.

  10. Attenuation of lymphocyte immune responses during Mycobacterium avium complex-induced lung disease due to increasing expression of programmed death-1 on lymphocytes

    PubMed Central

    Shu, Chin-Chung; Wang, Jann-Yuan; Wu, Ming-Fang; Wu, Chen-Tu; Lai, Hsin-Chih; Lee, Li-Na; Chiang, Bor-Luen; Yu, Chong-Jen

    2017-01-01

    Mycobacterium avium complex-induced lung disease (MAC-LD) becomes important due to its increasing prevalence. Attenuated cellular immunity associated with programmed cell death (PD)–1 may play a pathophysiological role in MAC-LD but lacks of investigation. We enrolled 80 participants in this prospective study, including 50 with MAC-LD and 30 healthy controls. Peripheral blood mononuclear cells (PBMCs), lymphocytes and monocyte-derived macrophages were used for MAC antigen stimulation. Patients with MAC-LD had lower tumor necrosis factor-α and interferon-γ responses compared to the healthy controls in PBMC stimulation assays with MAC bacilli. These responses improved after MAC treatment. The PD-1 and PD ligand expressions and apoptosis were higher in the lymphocytes of the patients with MAC-LD compared to the controls. Both PD-1 and apoptosis on T lymphocytes were significantly increased in the patients with MAC-LD, either by direct MAC stimulation or by MAC-primed macrophage activation. Partially blocking PD-1 and the PD ligand with antagonizing antibodies in the stimulation assay significantly increased the cytokine production of IFN-γ and decreased the apoptosis on T lymphocytes. In conclusion, the patients with MAC-LD have attenuated lymphocyte immunity, which might be associated with increasing activation of PD-1 and PD-1 ligand. Regulating such activation might improve the lymphocytic secretion of IFN-γ and reduce apoptosis. PMID:28169347

  11. 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.

  12. Description and assessment of a registration-based approach to include bones for attenuation correction of whole-body PET/MRI.

    PubMed

    Marshall, Harry R; Patrick, John; Laidley, David; Prato, Frank S; Butler, John; Théberge, Jean; Thompson, R Terry; Stodilka, Robert Z

    2013-08-01

    Attenuation correction for whole-body PET/MRI is challenging. Most commercial systems compute the attenuation map from MRI using a four-tissue segmentation approach. Bones, the most electron-dense tissue, are neglected because they are difficult to segment. In this work, the authors build on this segmentation approach by adding bones using a registration technique and assessing its performance on human PET images. Twelve oncology patients were imaged with FDG PET/CT and MRI using a Turbo-FLASH pulse sequence. A database of 121 attenuation correction quality CT scans was also collected. Each patient MRI was compared to the CT database via weighted heuristic measures to find the "most similar" CT in terms of body geometry. The similar CT was aligned to the MRI with a deformable registration method. Two MRI-based attenuation maps were computed. One was a standard four-tissue segmentation (air, lung, fat, and lean tissue) using basic image processing techniques. The other was identical, except the bones from the aligned CT were added. The PET data were reconstructed with the patient's CT-based attenuation map (the silver standard) and both MRI-based attenuation maps. The relative errors of the MRI-based attenuation corrections were computed in 14 standardized volumes of interest, in lesions, and over whole tissues. The squared Pearson correlation coefficient was also calculated over whole tissues. Statistical testing was done with ANOVAs and paired t-tests. The MRI-based attenuation correction ignoring bone had relative errors ranging from -37% to -8% in volumes of interest containing bone. By including bone, the magnitude of the relative error was reduced in all cases (p<0.001), ranging from -3% to 4%. Further, the relative error in volumes of interest adjacent to bone was improved from a mean of -7.5% to 2% (p<0.001). In the other seven volumes of interest, including bone reduced the magnitude of relative error in three cases (p<0.001), had no effect in three cases

  13. 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.

  14. 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.

  15. Dispersion and Attenuation Due to Scattering from Heterogeneities of the Frame Bulk Modulus of a Poroelastic Medium

    DTIC Science & Technology

    2010-02-19

    attenuation is a function of the Hurst exponent which characterizes the fractal het- erogeneity. Muller and Gurevich15,16 used statistical smoothing of...modified Bessel function of the third kind, Γ denotes the gamma function, and ν is the Hurst coefficient which is assumed to be 0 < ν ≤ 1. The three...The Hurst coefficient, ν, is ν = 0.1 (long-dashed line), ν = 0.5 (short-dashed line), and ν = 0.9 (long-short dashed line). In (a) the sound speed

  16. 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.

  17. A new three-dimensional exponential material model of the coronary arterial wall to include shear stress due to torsion.

    PubMed

    Van Epps, J Scott; Vorp, David A

    2008-10-01

    The biomechanical milieu of the coronary arteries is unique in that they experience mechanical deformations of twisting, bending, and stretching due to their tethering to the epicardial surface. Spatial variations in stresses caused by these deformations could account for the heterogeneity of atherosclerotic plaques within the coronary tree. The goal of this work was to utilize previously reported shear moduli to calculate a shear strain parameter for a Fung-type exponential model of the arterial wall and determine if this single constant can account for the observed behavior of arterial segments under torsion. A Fung-type exponential strain-energy function was adapted to include a torsional shear strain term. The material parameter for this term was determined from previously published data describing the relationship between shear modulus and circumferential stress and longitudinal stretch ratio. Values for the shear strain parameter were determined for three geometries representing the mean porcine left anterior descending coronary artery dimensions plus or minus one standard deviation. Finite element simulation of triaxial biomechanical testing was then used to validate the model. The mean value calculated for the shear strain parameter was 0.0759+/-0.0009 (N=3 geometries). In silico triaxial experiments demonstrated that the shear modulus is directly proportional to the applied pressure at a constant longitudinal stretch ratio and to the stretch ratio at a constant pressure. Shear moduli determined from these simulations showed excellent agreement to shear moduli reported in literature. Previously published models describing the torsional shear behavior of porcine coronary arteries require a total of six independent constants. We have reduced that description into a single parameter in a Fung-type exponential strain-energy model. This model will aid in the estimation of wall stress distributions of vascular segments undergoing torsion, as such information

  18. Bottom attenuation estimation using sound intensity fluctuations due to mode coupling by nonlinear internal waves in shallow water.

    PubMed

    Grigorev, Valery A; Katsnelson, Boris G; Lynch, James F

    2016-11-01

    Analyses of fluctuations of low frequency signals (300 ± 30 Hz) propagating in shallow water in the presence of nonlinear internal waves (NIWs) in the Shallow Water 2006 experiment are carried out. Signals were received by a vertical line array at a distance of ∼20 km from the source. A NIW train was moving totally inside of the acoustic track, and the angle between the wave front of the NIW and the acoustic track in the horizontal plane was ∼10°. It is shown that the spectrum of the sound intensity fluctuations contains peaks corresponding to the coupling of pairs of propagating modes. Analysis of spectra at different hydrophone depths, and also summed over depth allows the authors to estimate attenuation in the bottom sediments.

  19. Evidence that rifampicin can stimulate readthrough of transcriptional terminators in Escherichia coli, including the attenuator of the rpoBC operon.

    PubMed Central

    Newman, A J; Ma, J C; Howe, K M; Garner, I; Hayward, R S

    1982-01-01

    The genes encoding the beta and beta' subunits of RNA polymerase in E.coli, rpoB and rpoC, lie downstream of at least two ribosomal protein genes, rplJ (encoding L10) and rplL (L7/12), in a common operon. All four genes are served by promoter PL10, and an attenuator (partial terminator) of transcription, t1, lies between rplJL and rpoBC. Treatment of E.coli with rifampicin, under conditions producing partial inhibition of general RNA synthesis, can stimulate transcription of rpoBC. We have investigated the locus of this effect by fusing PL10 and t1 separately to galK, in suitable plasmids. Our studies of these fusions, and similar fusions involving transcriptional terminators derived from coliphage T7, indicate that low concentrations of rifampicin cause increased readthrough of several different transcriptional terminators in E.coli in vivo, including rpo t1. We discuss whether or not this unspecific mechanism is solely responsible for the observed stimulatory effects of the drug on rpoBC transcription. PMID:6296775

  20. Core-excitation energy calculations with a long-range corrected hybrid exchange-correlation functional including a short-range Gaussian attenuation (LCgau-BOP).

    PubMed

    Song, Jong-Won; Watson, Mark A; Nakata, Ayako; Hirao, Kimihiko

    2008-11-14

    We report the calculations of core-excitation energies of first-row atoms using the time-dependent density functional theory (DFT) and the long-range correction (LC) scheme for exchange-correlation functionals, including LC-BOP, Coulomb-attenuated method BLYP, and our recently developed LCgau-BOP method, which includes a flexible portion of short-range Hartree-Fock (HF) exchange through the inclusion of a Gaussian function in the LC scheme. We show that the LC scheme completely fails to improve the poor accuracy of conventional generalized gradient approximation functionals, while the LCgau scheme gives an accuracy which is an order of magnitude better than BLYP and significantly better than B3LYP. A reoptimization of the two parameters controlling the inclusion of short-range HF exchange in the LCgau method enables the errors to be reduced to the order of 0.1 eV which is competitive with the best DFT methods we are aware of. This reparametrization does not affect the LC scheme and therefore maintains the high accuracy of predicted reaction barrier heights. Moreover, while there is some loss in accuracy in thermochemical predictions compared to the previously optimized LCgau-BOP, rms errors in the atomization energies over the G2 test set are found to be comparable to B3LYP. Finally, we attempt to rationalize the success of the LC and LCgau schemes in terms of the well-known self-interaction error (SIE) of conventional functionals. To estimate the role of the SIE, we examine the total energy calculations for systems with a fractional number of electrons, not only in the highest occupied molecular orbital but also in the 1s-characterized core orbital. Our conclusion is that the inclusion of short-range HF exchange in LC-type functionals can significantly alleviate the problems of the SIE in the core region. In particular, we confirm that the absence of the SIE diagnostics in the core orbital energies correlates with the accurate prediction of core

  1. Anti-Osteoclastic Activity of Artemisia capillaris Thunb. Extract Depends upon Attenuation of Osteoclast Differentiation and Bone Resorption-Associated Acidification Due to Chlorogenic Acid, Hyperoside, and Scoparone

    PubMed Central

    Lee, Sang-Hyun; Lee, Jung-Yun; Kwon, Young-In; Jang, Hae-Dong

    2017-01-01

    The present study attempts to elucidate the anti-osteoporotic activity of Artemisia capillaris Thunb. in the form of anti-osteoclastic effect and responsible bioactive compounds. The contents of chlorogenic acid, caffeic acid, hyperoside, isoquercitrin, isochlorogenic acid A, and scoparone in Artemisia capillaris hydroethanolic extract (ACHE) were 38.53, 0.52, 4.07, 3.03, 13.90, and 6.59 mg/g, respectively. ACHE diminished osteoclast differentiation and bone resorption due to chlorogenic acid, hyperoside, and scoparone. In addition, ACHE attenuated acidification as well as reducing tumor necrosis factor receptor-associated factor 6 (TRAF6) expression and its association with vacuolar H+-adenosine triphosphatase (V-ATPase). Furthermore, chlorogenic acid, hyperoside, and scoparone from A. capillaris abrogated the association of V-ATPase with TRAF6, suggesting that the blockage of bone resorption by A. capillaris was partially mediated by reducing acidification through down-regulating interaction of V-ATPase with TRAF6 due to scoparone as well as chlorogenic acid and hyperoside. These results imply that the anti-osteoclastic effect of A. capillaris through down-regulating osteoclast differentiation and bone resorption may contribute to its anti-osteoporotic effect. PMID:28165389

  2. Anti-Osteoclastic Activity of Artemisia capillaris Thunb. Extract Depends upon Attenuation of Osteoclast Differentiation and Bone Resorption-Associated Acidification Due to Chlorogenic Acid, Hyperoside, and Scoparone.

    PubMed

    Lee, Sang-Hyun; Lee, Jung-Yun; Kwon, Young-In; Jang, Hae-Dong

    2017-02-04

    The present study attempts to elucidate the anti-osteoporotic activity of Artemisia capillaris Thunb. in the form of anti-osteoclastic effect and responsible bioactive compounds. The contents of chlorogenic acid, caffeic acid, hyperoside, isoquercitrin, isochlorogenic acid A, and scoparone in Artemisia capillaris hydroethanolic extract (ACHE) were 38.53, 0.52, 4.07, 3.03, 13.90, and 6.59 mg/g, respectively. ACHE diminished osteoclast differentiation and bone resorption due to chlorogenic acid, hyperoside, and scoparone. In addition, ACHE attenuated acidification as well as reducing tumor necrosis factor receptor-associated factor 6 (TRAF6) expression and its association with vacuolar H⁺-adenosine triphosphatase (V-ATPase). Furthermore, chlorogenic acid, hyperoside, and scoparone from A. capillaris abrogated the association of V-ATPase with TRAF6, suggesting that the blockage of bone resorption by A. capillaris was partially mediated by reducing acidification through down-regulating interaction of V-ATPase with TRAF6 due to scoparone as well as chlorogenic acid and hyperoside. These results imply that the anti-osteoclastic effect of A. capillaris through down-regulating osteoclast differentiation and bone resorption may contribute to its anti-osteoporotic effect.

  3. Risperidone-induced action potential prolongation is attenuated by increased repolarization reserve due to concomitant block of I(Ca,L).

    PubMed

    Christ, Torsten; Wettwer, Erich; Ravens, Ursula

    2005-05-01

    The neuroleptic risperidone is an effective blocker of the rapidly activating component of the delayed rectifier current (I(Kr)) and hence is expected to prolong cardiac action potential duration (APD). However, unlike with other typical I(Kr) blockers we failed to demonstrate a marked prolongation of late repolarization with risperidone. It is hypothesized that the APD-prolonging effect of risperidone is masked by the high repolarization reserve due to the prominent delayed rectifier currents I(Kr) and I(Ks) in guinea pig papillary muscle. Action potentials and force of contraction were recorded in isolated guinea pig papillary muscles. L-type calcium current I(Ca,L) and I(Kr) were measured using the standard patch clamp technique in single ventricular cardiomyocytes. Reduction of the repolarization reserve by the blocking of I(Ks) with chromanol 239B augmented the effect of the selective I(Kr) blocker E-4031, but not of risperidone, although both drugs completely blocked I(Kr). In contrast to E-4031 risperidone markedly reduced the force of contraction due to the partial blocking of I(Ca,L) in the same concentration range as required for block of I(Kr). Reduction of the repolarization reserve by the blocking of I(Ks) cannot exacerbate the APD-prolonging effect of risperidone. However, even incomplete concomitant blocking of I(Ca,L) attenuates the APD-prolonging effect of the complete blocking of I(Kr). This behaviour may explain the small APD-prolonging effect of risperidone despite the drug's robust blocking of I(Kr).

  4. Electromagnetic Waves Attenuation due to Rain: A Prediction Model for Terrestrial or L.O.S SHF and EHF Radio Communication Links

    NASA Astrophysics Data System (ADS)

    Moupfouma, Fidèle

    2009-06-01

    Because of the interest raised for SHF and EHF radio communications, the attenuation of electromagnetic waves by rain will always constitute a major concern for telecommunication engineers and scientists. The rain attenuation prediction models exposed in literature calculate the attenuation related to a given rain rate or else to a given percentage of time. The new model proposed in this paper, predicts with a good accuracy the percentage of time for which any given rain attenuation will be exceeded on terrestrial SHF, EHF radiowaves links, provided the rain rate R001 (mm/h) that represents rain rate value exceeded for 0.01% of time in the locality of interest is available. R001 (mm/h) data being available for most of the localities across the world in ITU-R data base, we may conclude that this new model proposed here, can be broadly and successfully used.

  5. ATTENUATION OF STATISTICAL RELATIONSHIPS FROM PM COMMUNITY TIME-SERIES EPIDEMIOLOGY DUE TO USE OF COMBINED, RATHER THAN SEPARATE, INDICATORS OF EXPOSURE AND MORTALITY

    EPA Science Inventory

    Attenuation of the statistical relationships between PM and health outcomes may arise from 1) combining exposure indicators, e.g., PM10 instead of PM2.5 and PM10-2.5 or 2) from combining different types of mortality. The Phoenix, AZ data base on air quality offers an opportunity...

  6. 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

    USDA-ARS?s Scientific Manuscript database

    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...

  7. ATTENUATION OF STATISTICAL RELATIONSHIPS FROM PM COMMUNITY TIME-SERIES EPIDEMIOLOGY DUE TO USE OF COMBINED, RATHER THAN SEPARATE, INDICATORS OF EXPOSURE AND MORTALITY

    EPA Science Inventory

    Attenuation of the statistical relationships between PM and health outcomes may arise from 1) combining exposure indicators, e.g., PM10 instead of PM2.5 and PM10-2.5 or 2) from combining different types of mortality. The Phoenix, AZ data base on air quality offers an opportunity...

  8. An efficient method to predict and include Bragg curve degradation due to lung-equivalent materials in Monte Carlo codes by applying a density modulation

    NASA Astrophysics Data System (ADS)

    Baumann, Kilian-Simon; Witt, Matthias; Weber, Uli; Engenhart-Cabillic, Rita; Zink, Klemens

    2017-05-01

    Sub-millimetre-sized heterogeneities such as lung parenchyma cause Bragg peak degradation which can lead to an underdose of the tumor and an overdose of healthy tissue when not accounted for in treatment planning. Since commonly used treatment-planning CTs do not resolve the fine structure of lungs, this degradation can hardly be considered. We present a mathematical model capable of predicting and describing Bragg peak degradation due to a lung-equivalent geometry consisting of sub-millimetre voxels filled with either lung tissue or air. The material characteristic ‘modulation power’ is introduced to quantify the Bragg peak degradation. A strategy was developed to transfer the modulating effects of such fine structures to rougher structures such as 2 mm thick CT voxels, which is the resolution of typically used CTs. This is done by using the modulation power to derive a density distribution applicable to these voxels. By replacing the previously used sub-millimetre voxels by 2 mm thick voxels filled with lung tissue and modulating the lung tissue’s density in each voxel individually, we were able to reproduce the Bragg peak degradation. Hence a solution is found to include Bragg curve degradation due to lung-equivalent materials in Monte Carlo-based treatment-planning systems.

  9. A quantitative three-dimensional dose attenuation analysis around Fletcher-Suit-Delclos due to stainless steel tube for high-dose-rate brachytherapy by Monte Carlo calculations.

    PubMed

    Parsai, E Ishmael; Zhang, Zhengdong; Feldmeier, John J

    2009-01-01

    The commercially available brachytherapy treatment-planning systems today, usually neglects the attenuation effect from stainless steel (SS) tube when Fletcher-Suit-Delclos (FSD) is used in treatment of cervical and endometrial cancers. This could lead to potential inaccuracies in computing dwell times and dose distribution. A more accurate analysis quantifying the level of attenuation for high-dose-rate (HDR) iridium 192 radionuclide ((192)Ir) source is presented through Monte Carlo simulation verified by measurement. In this investigation a general Monte Carlo N-Particles (MCNP) transport code was used to construct a typical geometry of FSD through simulation and compare the doses delivered to point A in Manchester System with and without the SS tubing. A quantitative assessment of inaccuracies in delivered dose vs. the computed dose is presented. In addition, this investigation expanded to examine the attenuation-corrected radial and anisotropy dose functions in a form parallel to the updated AAPM Task Group No. 43 Report (AAPM TG-43) formalism. This will delineate quantitatively the inaccuracies in dose distributions in three-dimensional space. The changes in dose deposition and distribution caused by increased attenuation coefficient resulted from presence of SS are quantified using MCNP Monte Carlo simulations in coupled photon/electron transport. The source geometry was that of the Vari Source wire model VS2000. The FSD was that of the Varian medical system. In this model, the bending angles of tandem and colpostats are 15 degrees and 120 degrees , respectively. We assigned 10 dwell positions to the tandem and 4 dwell positions to right and left colpostats or ovoids to represent a typical treatment case. Typical dose delivered to point A was determined according to Manchester dosimetry system. Based on our computations, the reduction of dose to point A was shown to be at least 3%. So this effect presented by SS-FSD systems on patient dose is of concern.

  10. 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

  11. 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

    2012-10-24

    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.

  12. 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…

  13. [Expression of high-level cephalosporinase due to mutation in the AmpC attenuator of a clinical Escherichia coli strain].

    PubMed

    Guan, Xi-zhou; Liu, You-ning; Luo, Yan-ping; She, Dan-yang; Lu, Si-jing; Zhou, Guang; Chen, Liang-an

    2006-03-07

    To study the resistant phenotype of a clinical strain of Escherichia coli and to explore the effect of its attenuator mutation on AmpC expression. A clinical strain of Escherichia coli 20022 (ECO20022) resistant to cefoxitin was isolated clinically. The phenotype was examined by three-dimensional methods, isoelectric focusing (IEF), and microdilution method. The regulator genes of ECO20022 were amplified and sequenced, and the difference between them was analyzed by BLAST method. Then the regulator genes were cloned into pCAT3-basic vector (a promoterless reporter gene vector). Microdilution method was used to detect the minimal inhibitory concentration (MIC) of chloramphenicol and ampicillin to this strain with E. coli ATCC25922 as quality control bacterium. ELISA was used to detect the content of chloramphenicol acetyl transferase (CAT). Compared to the standard E. coli K-12, there were four base substitutions, i.e., 22C-T, 26, 27TA-GT, and 32G-A in the attenuator region of ECO20022. Three-dimensional method showed that this strain was high AmpC-producing. IEF found that it produced three beta-lactamases with the values of PI of 5.4, 8.2, and 9.0 respectively. The beta-lactamase with the PI of 9.0 could be inhibited by cloxacillin but not by clavulanate. The strain was resistant to not only most of third generation cephalosporins, but also to cefepime; however it was still susceptible to carbapenem. The secondary structure of the attenuator RNA of ECO20022 was different from the traditional structure of E. coli K-12. The regulator gene was successfully cloned into pCAT3-basic vector and direct and indirect tests indicated that this regulator gene enhanced the CAT expressing level as much as 10 times that of Escherichia coli K-12. AmpC attenuator mutation leads to high AmpC expression in Escherichia coli, resulting in a significant rise of resistance level to beta-lactamase and a great menace to clinical antibiotic therapy.

  14. Analysis of the Attenuation Characteristics of an Elastic Wave Due to the Wave-Induced Fluid Flow in Fractured Porous Media

    NASA Astrophysics Data System (ADS)

    Wang, Ding; Wang, Li-Ji; Zhang, Mei-Gen

    2014-04-01

    A theoretical model is presented to describe the elastic wave propagation characteristics in porous media of periodically arranged fractures. The effects of fracture geometric parameters on a compressional wave (p-wave) are considered through analysis of the wave induced fluid flow (WIFF) process between the fractures and the background media. The diffusion equation in porous media is used to reveal how the entire diffusion process affects the wave propagation. When the thickness proportion of fractures tends to 0 and 1, the WIFF does not take place almost between fractures and background matrix porosity, and therefore the media elasticity modulus is perfectly elastic. When the fracture thickness fraction achieves a certain value, the peak of the attenuation curve reaches the maximum value at a particular frequency, which is controlled by the fluid mass conservation and stress continuity conditions on each fracture boundary. That is, the inter-coupling of fluid diffusion between the adjacent layers is important for waves attenuation. Physically speaking, the dissipation of a wave is associated with the fluid flux essentially.

  15. Microwave variable waveguide attenuator.

    PubMed

    Fabeni, P; Mugnai, D; Pazzi, G P; Ranfagni, A

    2008-06-01

    A new type of cutoff attenuator is presented. The attenuator works in the X-band in conditions of almost perfect matching. This means that the phase of the wave, which propagates inside the guide, does not suffer sensible variation in the passage between X- and K(u)-bands. Moreover, the attenuator works directly in the X-band, avoiding the passage between waveguide and cable, thus eliminating spurious effects due to this (double) passage. Experimental results of attenuation and dephasing using a prototype are also presented.

  16. [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.

  17. 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

    PubMed Central

    Bearson, Bradley L.; Bearson, Shawn M. D.; Kich, Jalusa D.; Lee, In Soo

    2014-01-01

    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 rfaH, the gene encoding the RfaH antiterminator that prevents premature termination of long mRNA transcripts. Pigs inoculated with wild-type S. Typhimurium exhibited a significant elevation in average body temperature (fever) at 1 and 2 days post-inoculation; rfaH-inoculated pigs did not (n = 5/group). During the 7-day trial, a significant reduction of Salmonella in the feces, tonsils, and cecum were observed in the rfaH-inoculated pigs compared to wild-type inoculated pigs. To determine whether vaccination with the rfaH mutant could provide protection against wild-type S. Typhimurium challenge, two groups of pigs (n = 14/group) were intranasally inoculated with either the rfaH mutant or a PBS placebo at 6 and 8 weeks of age and challenged with the parental, wild-type S. Typhimurium at 11 weeks of age. The average body temperature was significantly elevated in the mock-vaccinated pigs at 1 and 2 days post-challenge, but not in the rfaH-vaccinated pigs. Fecal shedding at 2 and 3 days post-challenge and colonization of intestinal tract tissues at 7 days post-challenge by wild-type S. Typhimurium was significantly reduced in the rfaH-vaccinated pigs compared to mock-vaccinated pigs. Serological analysis using the IDEXX HerdChek Swine Salmonella Test Kit indicated that vaccination with the rfaH mutant did not stimulate an immune response against LPS. These results indicate that vaccination of swine with the attenuated rfaH mutant confers protection against challenge with virulent S. Typhimurium but does not interfere with herd level monitoring for Salmonella spp., thereby allowing for differentiation of infected from vaccinated animals (DIVA). PMID

  18. Change in subcutaneous adipose tissue metabolism and gene network expression during the transition period in dairy cows, including differences due to sire genetic merit.

    PubMed

    Khan, M J; Hosseini, A; Burrell, S; Rocco, S M; McNamara, J P; Loor, J J

    2013-04-01

    Adipose metabolism is an essential contributor to the efficiency of milk production, and metabolism is controlled by several mechanisms, including gene expression of critical proteins; therefore, the objective of this study was to determine how lactational state and the genetic merit of dairy cattle affects adipose tissue (AT) metabolism and mRNA expression of genes known to control metabolism. Animals of high (HGM) and low genetic merit (LGM) were fed to requirements, and weekly dry matter intake, milk production, blood glucose, and nonesterified fatty acids were measured. Subcutaneous AT biopsies were collected at -21, 7, 28 and 56 d in milk (DIM). The mRNA expression of genes coding for lipogenic enzymes [phosphoenolpyruvate carboxykinase 1 (soluble) (PCK1), fatty acid synthase (FASN), diacylglycerol O-acyltransferase 2 (DGAT2), and stearoyl-coenzyme A desaturase (SCD)], transcription regulators [peroxisome proliferator-activated receptor γ (PPARG), thyroid hormone responsive (THRSP), wingless-type MMTV integration site family, member 10B (WNT10B), sterol regulatory element binding transcription factor 1 (SREBF1), and adiponectin (ADIPOQ)], lipolytic enzymes [hormone-sensitive lipase (LIPE), patatin-like phospholipase domain containing 2 (PNPLA2), monoglyceride lipase (MGLL), adrenoceptor β-2 (ADRB2), adipose differentiation-related protein (ADFP), and α-β-hydrolase domain containing 5 (ABHD5)], and genes controlling the sensing of intracellular energy [phosphodiesterase 3A (PDE3A); PDE3B; protein kinase, AMP-activated, α-1 catalytic subunit (PRKAA1); PRKAA2; and growth hormone receptor (GHR)] was measured. Dry matter intake, blood glucose, and nonesterified fatty acid concentrations did not differ between genetic merit groups. Milk production was greater for HGM cows from 6 to 8 wk postpartum. As expected, the rates of lipogenesis decreased in early lactation, whereas stimulated lipolysis increased. At 7 DIM, lipogenesis in HGM cows increased as a function

  19. Blockage of Autophagy in C6 Glioma Cells Enhanced Radiosensitivity Possibly by Attenuating DNA-PK-Dependent DSB Due to Limited Ku Nuclear Translocation and DNA Binding.

    PubMed

    Liu, C; He, W; Jin, M; Li, H; Xu, H; Liu, H; Yang, K; Zhang, T; Wu, G; Ren, J

    2015-01-01

    Glioblastoma multiforme (GBM) is the most lethal brain tumor and notorious for its resistance to ionizing radiation (IR). Recent evidence suggests that one possible mechanism that enables resistance to IR and protects cells against therapeutic stress is cellular autophagy. The molecular basis for this pro-survival function, however, remains elusive. Herein, we report a molecular mechanism by which IR-induced autophagy accelerates the repair of DNA double-strand breaks (DSB). We demonstrate that IR induces the accumulation of autophagosomes, which is accompanied by elevated expression of autophagyrelated genes beclin-1, atg5, atg7, and atg12. Beclin-1 knockdown impaired the induction of IR-mediated autophagy and significantly sensitized glioma cells to radiation therapy in vitro and in vivo. Furthermore, our data is the first to demonstrate that the radiosensitizing effect of beclin-1 knockdown may result from the disruption of nuclear translocation and DNA binding activity of Ku proteins and consequent attenuation of DSB repair. Our findings help advance our understanding of the molecular mechanisms underlying IR-induced autophagy and provide a promising adjunctive therapeutic strategy for the radiosensitization of malignant glioma.

  20. Caprylic triglyceride as a novel therapeutic approach to effectively improve the performance and attenuate the symptoms due to the motor neuron loss in ALS disease.

    PubMed

    Zhao, Wei; Varghese, Merina; Vempati, Prashant; Dzhun, Anastasiya; Cheng, Alice; Wang, Jun; Lange, Dale; Bilski, Amanda; Faravelli, Irene; Pasinetti, Giulio Maria

    2012-01-01

    Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder of motor neurons causing progressive muscle weakness, paralysis, and finally death. ALS patients suffer from asthenia and their progressive weakness negatively impacts quality of life, limiting their daily activities. They have impaired energy balance linked to lower activity of mitochondrial electron transport chain enzymes in ALS spinal cord, suggesting that improving mitochondrial function may present a therapeutic approach for ALS. When fed a ketogenic diet, the G93A ALS mouse shows a significant increase in serum ketones as well as a significantly slower progression of weakness and lower mortality rate. In this study, we treated SOD1-G93A mice with caprylic triglyceride, a medium chain triglyceride that is metabolized into ketone bodies and can serve as an alternate energy substrate for neuronal metabolism. Treatment with caprylic triglyceride attenuated progression of weakness and protected spinal cord motor neuron loss in SOD1-G93A transgenic animals, significantly improving their performance even though there was no significant benefit regarding the survival of the ALS transgenic animals. We found that caprylic triglyceride significantly promoted the mitochondrial oxygen consumption rate in vivo. Our results demonstrated that caprylic triglyceride alleviates ALS-type motor impairment through restoration of energy metabolism in SOD1-G93A ALS mice, especially during the overt stage of the disease. These data indicate the feasibility of using caprylic acid as an easily administered treatment with a high impact on the quality of life of ALS patients.

  1. Caprylic Triglyceride as a Novel Therapeutic Approach to Effectively Improve the Performance and Attenuate the Symptoms Due to the Motor Neuron Loss in ALS Disease

    PubMed Central

    Zhao, Wei; Varghese, Merina; Vempati, Prashant; Dzhun, Anastasiya; Cheng, Alice; Wang, Jun; Lange, Dale; Bilski, Amanda; Faravelli, Irene; Pasinetti, Giulio Maria

    2012-01-01

    Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder of motor neurons causing progressive muscle weakness, paralysis, and finally death. ALS patients suffer from asthenia and their progressive weakness negatively impacts quality of life, limiting their daily activities. They have impaired energy balance linked to lower activity of mitochondrial electron transport chain enzymes in ALS spinal cord, suggesting that improving mitochondrial function may present a therapeutic approach for ALS. When fed a ketogenic diet, the G93A ALS mouse shows a significant increase in serum ketones as well as a significantly slower progression of weakness and lower mortality rate. In this study, we treated SOD1-G93A mice with caprylic triglyceride, a medium chain triglyceride that is metabolized into ketone bodies and can serve as an alternate energy substrate for neuronal metabolism. Treatment with caprylic triglyceride attenuated progression of weakness and protected spinal cord motor neuron loss in SOD1-G93A transgenic animals, significantly improving their performance even though there was no significant benefit regarding the survival of the ALS transgenic animals. We found that caprylic triglyceride significantly promoted the mitochondrial oxygen consumption rate in vivo. Our results demonstrated that caprylic triglyceride alleviates ALS-type motor impairment through restoration of energy metabolism in SOD1-G93A ALS mice, especially during the overt stage of the disease. These data indicate the feasibility of using caprylic acid as an easily administered treatment with a high impact on the quality of life of ALS patients. PMID:23145119

  2. Antioxidant Peroxiredoxin 6 protein rescues toxicity due to oxidative stress and cellular hypoxia in vitro, and attenuates prion-related pathology in vivo

    PubMed Central

    Asuni, Ayodeji. A.; Guridi, Maitea; Sanchez, Sandrine; Sadowski, Martin J

    2015-01-01

    Protein misfolding, mitochondrial dysfunction and oxidative stress are common pathomechanisms that underlie neurodegenerative diseases. In prion disease, central to these processes is the post-translational transformation of cellular prion protein (PrPc) to the aberrant conformationally altered isoform; PrPSc. This can trigger oxidative reactions and impair mitochondrial function by increasing levels of peroxynitrite, causing damage through formation of hydroxyl radicals or via nitration of tyrosine residues on proteins. The 6 member Peroxiredoxin (Prdx) family of redox proteins are thought to be critical protectors against oxidative stress via reduction of H2O2, hydroperoxides and peroxynitrite. In our in vitro studies cellular metabolism of SK-N-SH human neuroblastoma cells was significantly decreased in the presence of H2O2 (oxidative stressor) or CoCl2 (cellular hypoxia), but was rescued by treatment with exogenous Prdx6, suggesting that its protective action is in part mediated through a direct action. We also show that CoCl2-induced apoptosis was significantly decreased by treatment with exogenous Prdx6. We proposed a redox regulator role for Prdx6 in regulating and maintaining cellular homeostasis via its ability to control ROS levels that could otherwise accelerate the emergence of prion-related neuropathology. To confirm this, we established prion disease in mice with and without astrocyte-specific antioxidant protein Prdx6, and demonstrated that expression of Prdx6 protein in Prdx6 Tg ME7-animals reduced severity of the behavioural deficit, decreased neuropathology and increased survival time compared to Prdx6 KO ME7-animals. We conclude that antioxidant Prdx6 attenuates prion-related neuropathology, and propose that augmentation of endogenous Prdx6 protein represents an attractive adjunct therapeutic approach for neurodegenerative diseases. PMID:26265052

  3. [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.

  4. 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.

  5. Aphasia due to lesions confined to the right hemisphere in right handed patients: a review of the literature including the Italian cases.

    PubMed

    Faglia, L; Rottoli, M R; Vignolo, L A

    1990-04-01

    We review most of the work published, to our knowledge, between 1880 and 1988 on aphasia due to right cerebral lesions in right-handed patients ("crossed aphasia"). We summarize the 87 cases found in chronological order within defined groups, dealing in greater detail with the less well-known cases in English-language publications and with the cases from other sources that we consider most representative and convincing. The 87 cases fall into three groups on the following criteria: right-handedness (on standardized tests), absence of left-handers in the family, left hemisphere integrity. Group 1 comprises cases that are unreliable because the handedness data are missing and/or because left hemisphere lesions were known to be present or probably were so. Group 2 comprises cases with full clinical data but no formal test of handedness, with familial cases of left-handedness and/or without satisfactory evidence of left hemisphere integrity. Groups 3 comprises the 26 reliable cases, that is those with proven right-handedness, no left-handers in the family and with proven hemisphere integrity. We discuss the implications of these cases.

  6. 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 ...

  7. 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 ...

  8. Dietary acid reduction with fruits and vegetables or bicarbonate attenuates kidney injury in patients with a moderately reduced glomerular filtration rate due to hypertensive nephropathy.

    PubMed

    Goraya, Nimrit; Simoni, Jan; Jo, Chanhee; Wesson, Donald E

    2012-01-01

    The neutralization of dietary acid with sodium bicarbonate decreases kidney injury and slows the decline of the glomerular filtration rate (GFR) in animals and patients with chronic kidney disease. The sodium intake, however, could be problematic in patients with reduced GFR. As alkali-induced dietary protein decreased kidney injury in animals, we compared the efficacy of alkali-inducing fruits and vegetables with oral sodium bicarbonate to diminish kidney injury in patients with hypertensive nephropathy at stage 1 or 2 estimated GFR. All patients were evaluated 30 days after no intervention; daily oral sodium bicarbonate; or fruits and vegetables in amounts calculated to reduce dietary acid by half. All patients had 6 months of antihypertensive control by angiotensin-converting enzyme inhibition before and during these studies, and otherwise ate ad lib. Indices of kidney injury were not changed in the stage 1 group. By contrast, each treatment of stage 2 patients decreased urinary albumin, N-acetyl β-D-glucosaminidase, and transforming growth factor β from the controls to a similar extent. Thus, a reduction in dietary acid decreased kidney injury in patients with moderately reduced eGFR due to hypertensive nephropathy and that with fruits and vegetables was comparable to sodium bicarbonate. Fruits and vegetables appear to be an effective kidney protective adjunct to blood pressure reduction and angiotensin-converting enzyme inhibition in hypertensive and possibly other nephropathies.

  9. Clinically relevant fluoroquinolone resistance due to constitutive overexpression of the PatAB ABC transporter in Streptococcus pneumoniae is conferred by disruption of a transcriptional attenuator.

    PubMed

    Baylay, Alison J; Piddock, Laura J V

    2015-03-01

    Constitutive overexpression of patAB has been observed in several unrelated fluoroquinolone-resistant laboratory mutants and clinical isolates; therefore, we sought to identify the cause of this overexpression. Constitutive patAB overexpression in two clinical isolates and a laboratory-selected mutant was investigated using a whole-genome transformation approach. To determine the effect of the detected terminator mutations, the WT and mutated patA leader sequences were cloned upstream of a GFP reporter. Finally, mutation of the opposing base in the stem-loop structure was carried out. We identified three novel mutations causing up-regulation of patAB. All three of these were located in the upstream region of patA and affected the same Rho-independent transcriptional terminator structure. Each mutation was predicted to destabilize the terminator stem-loop to a different degree, and there was a strong correlation between predicted terminator stability and patAB expression level. Using a GFP reporter of patA transcription, these terminator mutations led to increased transcription of a downstream gene. For one mutant sequence, terminator stability could be restored by mutation of the opposing base in the stem-loop structure, demonstrating that transcriptional suppression of patAB is mediated by the terminator stem-loop structure. This study showed that a mutation in a Rho-independent transcriptional terminator structure confers overexpression of patAB and fluoroquinolone resistance. Understanding how levels of the PatAB efflux pump are regulated increases our knowledge of pneumococcal biology and how the pneumococcus can respond to various stresses, including antimicrobials. © The Author 2014. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy.

  10. 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.

  11. Attenuator And Conditioner

    SciTech Connect

    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.

  12. 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.

  13. Radiofrequency attenuator and method

    DOEpatents

    Warner, Benjamin P [Los Alamos, NM; McCleskey, T Mark [Los Alamos, NM; Burrell, Anthony K [Los Alamos, NM; Agrawal, Anoop [Tucson, AZ; Hall, Simon B [Palmerston North, NZ

    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.

  14. Theoretical and numerical results on effects of attenuation on correlation functions of ambient seismic noise

    NASA Astrophysics Data System (ADS)

    Liu, Xin; Ben-Zion, Yehuda

    2013-09-01

    We study analytically and numerically effects of attenuation on cross-correlation functions of ambient noise in a 2-D model with different attenuation constants between and outside a pair of stations. The attenuation is accounted for by quality factor Q(ω) and complex phase velocity. The analytical results are derived for isotropic far-field source distribution assuming the Fresnel approximation and mild attenuation. More general situations including cases with non-isotropic source distributions are examined with numerical simulations. The results show that homogeneous attenuation in the interstation regions produces symmetric amplitude decay of the causal and anticausal parts of the noise cross-correlation function. The attenuation between the receivers and far-field sources generates symmetric exponential amplitude decay and may also cause asymmetric reduction of the causal/anticausal parts that increases with frequency. This frequency dependence can be used to distinguish asymmetric amplitudes due to attenuation from frequency-independent asymmetry in noise correlations generated by non-isotropic source distribution. The attenuations both between and outside station pairs also produce phase shifts that could affect measurements of group and phase velocities. In terms of noise cross-spectra, the interstation attenuation is governed by Struve functions while the attenuation between the far-field sources and receivers is associated with exponential decay and the imaginary part of complex Bessel function. These results are fundamentally different from previous studies of attenuated coherency that append the Bessel function with an exponential decay that depends on the interstation distance.

  15. 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.

  16. 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.

  17. 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.

  18. Rocket engine nozzle attenuator

    NASA Astrophysics Data System (ADS)

    Lewis, David A.

    1993-01-01

    The function of a rocket engine nozzle is to expand the hot engine exhaust gases down to ambient pressure, transforming thermal energy to directed kinetic energy in order to produce thrust. Considering nozzle design, there is an optimum nozzle shape and length, the bell-shaped or contour nozzle. The reason for this specific contour is that the nozzle must be designed in such a manner that the expansion shock waves emanating from the nozzle throat region coincide, and thus diminish the compression effects accompanying the reorientation of flow in the center region of the expansion section. A rocket nozzle must absorb a variety of loads caused by such shocks due to thermal expansion and contraction, as well as shocks from sudden pressurization at startup, and flight accelerations. A rocket engine nozzle is provided which is capable of attenuating nozzle vibrations generated therein during use. The nozzle includes an annular closed chamber surrounding the nozzle adjacent to its gas exhaust end. Within the chamber is a dense but unrestricted particulate mass capable of undergoing frictional movement within the chamber.

  19. Study of ultrasonic attenuation on aging precipitation in a Ti-6Al-4V alloy

    NASA Astrophysics Data System (ADS)

    Carreón, Héctor; Dueñas, Antonio; Ruiz, Alberto; Barrera, Gerardo

    2017-02-01

    Ti-6Al-4V alloy with different microstructures was investigated by means of ultrasonic attenuation measurements. Widmanstätten and equiaxed microstructures were obtaining by heat treating a Ti-6Al-4V alloy. These two microstructures were over-aged at 545°C at different aging times. In order to find out the factors affecting the variation in the ultrasonic attenuation, the heat treated samples were examined by optical microscopy (OM) and (SEM) scanning electron microscopy. Based on the theory of ultrasonic attenuation in a solid media, the mechanisms of ultrasonic attenuation in the Ti-6Al-4V alloy with different microstructures were analyzed. It was found that in both cases with Widmanstätten and equiaxed microstructures, the ultrasonic attenuation increased with frequency. After aging, the ultrasonic attenuation was mainly attributed to the scattering loss which included the stochastic and the Rayleigh scattering due to the interaction between the ultrasonic wave and the material microstructure.

  20. 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.

  1. Orally administered selective TRPV1 antagonist, JTS-653, attenuates chronic pain refractory to non-steroidal anti-inflammatory drugs in rats and mice including post-herpetic pain.

    PubMed

    Kitagawa, Yoshihiro; Tamai, Isao; Hamada, Yuji; Usui, Kenji; Wada, Masashi; Sakata, Masahiro; Matsushita, Mutsuyoshi

    2013-01-01

    Chronic pain refractory to non-steroidal anti-inflammatory drugs (NSAIDs) is a major problem and drugs for such pain are needed. Many studies suggest that transient receptor potential vanilloid type 1 (TRPV1) is associated with NSAID-refractory chronic pain. Therefore, we investigated the involvement of TRPV1 in NSAID-refractory chronic pain using experimental models for NSAID-refractory chronic pain reflecting severe arthritic and postherpetic pain. The selective TRPV1 antagonist JTS-653 {(3S)-3-(hydroxymethyl)-4-(5-methylpyridin-2-yl)-N-[6-(2,2,2-trifluoroethoxy)pyridin-3-yl]-3,4-dihydro-2H-benzo[b][1,4]oxazine-8-carboxamide} reversed mechanical hyperalgesia on day 7 after injection of complete-Freund-adjuvant into the hindpaw in rats at 0.3 mg/kg, whereas indomethacin showed no effect. JTS-653 reduced chronic pain at 0.3 mg/kg in herpes simplex virus-1-inoculated mice that has been reported as NSAID-refractory pain. JTS-653 partially attenuated mechanical hyperalgesia in the L5 spinal nerve ligation model in rats at 0.3 mg/kg, whereas indomethacin showed no effect. Both JTS-653 and indomethacin reduced formalin-induced pain in the second phase, whereas they showed no effect in the first phase. JTS-653 did not affect the nociception of noxious thermal and mechanical stimuli and motor coordination in normal rats. These findings demonstrate the TRPV1 involvement in NSAID-refractory chronic pain reflecting severe arthritic and postherpetic pain. TRPV1 antagonists would be useful for the treatment of NSAID-refractory chronic pain.

  2. Variable anelastic attenuation and site effect in estimating source parameters of various major earthquakes including M w 7.8 Nepal and M w 7.5 Hindu kush earthquake by using far-field strong-motion data

    NASA Astrophysics Data System (ADS)

    Kumar, Naresh; Kumar, Parveen; Chauhan, Vishal; Hazarika, Devajit

    2016-12-01

    Strong-motion records of recent Gorkha Nepal earthquake (M w 7.8), its strong aftershocks and seismic events of Hindu kush region have been analysed for estimation of source parameters. The M w 7.8 Gorkha Nepal earthquake of 25 April 2015 and its six aftershocks of magnitude range 5.3-7.3 are recorded at Multi-Parametric Geophysical Observatory, Ghuttu, Garhwal Himalaya (India) >600 km west from the epicentre of main shock of Gorkha earthquake. The acceleration data of eight earthquakes occurred in the Hindu kush region also recorded at this observatory which is located >1000 km east from the epicentre of M w 7.5 Hindu kush earthquake on 26 October 2015. The shear wave spectra of acceleration record are corrected for the possible effects of anelastic attenuation at both source and recording site as well as for site amplification. The strong-motion data of six local earthquakes are used to estimate the site amplification and the shear wave quality factor (Q β) at recording site. The frequency-dependent Q β(f) = 124f 0.98 is computed at Ghuttu station by using inversion technique. The corrected spectrum is compared with theoretical spectrum obtained from Brune's circular model for the horizontal components using grid search algorithm. Computed seismic moment, stress drop and source radius of the earthquakes used in this work range 8.20 × 1016-5.72 × 1020 Nm, 7.1-50.6 bars and 3.55-36.70 km, respectively. The results match with the available values obtained by other agencies.

  3. Less invasive corrective surgery using oblique lateral interbody fusion (OLIF) including L5-S1 fusion for severe lumbar kyphoscoliosis due to L4 compression fracture in a patient with Parkinson's disease: a case report.

    PubMed

    Wakita, Hiromasa; Shiga, Yasuhiro; Ohtori, Seiji; Kubota, Go; Inage, Kazuhide; Sainoh, Takeshi; Sato, Jun; Fujimoto, Kazuki; Yamauchi, Kazuyo; Nakamura, Junichi; Takahashi, Kazuhisa; Toyone, Tomoaki; Aoki, Yasuchika; Inoue, Gen; Miyagi, Masayuki; Orita, Sumihisa

    2015-04-07

    Corrective surgery for kyphoscoliosis patients tend to be highly invasive due to osteotomy. The present case introduce less invasive corrective surgery using anterior oblique lateral interbody fusion (OLIF) technique. An 80-year-old Japanese man with a history of Parkinson's disease presented to our hospital because of severe kyphoscoliosis and gait disturbance. Considering the postsurgical complications due to osteotomy, we performed an anterior-posterior combined corrective fusion surgery: OLIF of Lumbar (L) 2-3, L3-4, and L4-5 (Medtronic Sofamor Danek, Memphis, TN, USA) followed by L5-Sacral (S) 1 anterior lumbar fusion via the OLIF approach using an anterior intervertebral cage, and posterior L3-4 and L4-5 facetectomy and posterior fusion using percutaneous pedicle screws from Thoracic (T) 10 to S1 with a T-9 hook system. The surgery was performed in a less invasive manner with no osteotomy, and it improved the sagittal alignments with moderate restoration, which improved the patient's posture and gait disturbance. The patient showed transient muscle weakness of proximal lower extremity contralateral side to the surgical site, which fully recovered by physical rehabilitation 3 months after the surgery. The surgical corrective procedure using the minimally invasive OLIF method including L5-S1 fusion showed a great advantage in treating degenerative kyphoscoliosis in a Parkinson's disease patient in its less-invasive approac.

  4. 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.

  5. Guided wave attenuation in pipes buried in sand

    NASA Astrophysics Data System (ADS)

    Leinov, Eli; Cawley, Peter; Lowe, Michael JS

    2015-03-01

    Long-range ultrasonic guided wave testing of pipelines is used routinely for detection of corrosion defects in a variety of industries, e.g. petrochemical and energy. When the method is applied to pipelines that are buried in soil, test ranges tend to be significantly compromised compared to those achieved for pipelines above ground because of the attenuation of the guided wave, due to energy leaking into the embedding soil. The attenuation characteristics of guided wave propagation in a pipe buried in sand are investigated using a full scale experimental rig. The apparatus consists of an 8"-diameter, 6-meters long steel pipe embedded over 3 meters in a rectangular container filled with sand and fitted with an air-bladder for the application of overburden pressure. Measurements of the attenuation of the T(0,1) and L(0,2) guided wave modes over a range of sand conditions, including loose, compacted, water saturated and drained, are presented. Attenuation values are found to be in the range of 1-5.5 dB/m. The application of overburden pressure modifies the compaction of the sand and increases the attenuation. The attenuation decreases in the fully water-saturated sand, while it increases in drained sand to values comparable with those obtained for the compacted sand. The attenuation behavior of the torsional guided wave mode is found not to be captured by a uniform soil model; comparison with predictions obtained with the Disperse software suggest that this is likely to be due to a layer of sand adhering to the surface of the pipe.

  6. 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.

  7. In inflammatory reactive astrocytes co-cultured with brain endothelial cells nicotine-evoked Ca(2+) transients are attenuated due to interleukin-1beta release and rearrangement of actin filaments.

    PubMed

    Delbro, D; Westerlund, A; Björklund, U; Hansson, E

    2009-03-17

    The aim of this study was to investigate whether nicotine acetylcholine receptors (nAChRs) are expressed in a more pronounced way in astrocytes co-cultured with microvascular endothelial cells from adult rat brain, compared with monocultured astrocytes, as a sign of a more developed signal transduction system. Also investigated was whether nicotine plays a role in the control of neuroinflammatory reactivity in astrocytes. Ca(2+) imaging experiments were performed using cells loaded with the Ca(2+) indicator Fura-2/AM. Co-cultured astrocytes responded to lower concentrations of nicotine than did monocultured astrocytes, indicating that they are more sensitive to nicotine. Co-cultured astrocytes also expressed a higher selectivity for alpha7nAChR and alpha4/beta2 subunits and evoked higher Ca(2+) transients compared with monocultured astrocytes. The Ca(2+) transients referred to are activators of Ca(2+)-induced Ca(2+) release from intracellular stores, both IP(3) and ryanodine, triggered by influx through receptor channels. The nicotine-induced Ca(2+) transients were attenuated after incubation with the inflammatory mediator lipopolysaccharide (LPS), but were not attenuated after incubation with the pain-transmitting peptides substance P and calcitonin-gene-related peptide, nor with the infection and inflammation stress mediator, leptin. Furthermore, LPS-induced release of interleukin-1beta (IL-1beta) measured by enzyme-linked immunosorbent assay (ELISA) was more pronounced in co-cultured versus monocultured astrocytes. Incubation with both LPS and IL-1beta further attenuated nicotine-induced Ca(2+) response. We also found that LPS and IL-1beta induced rearrangement of the F-actin filaments, as measured with an Alexa488-conjugated phalloidin probe. The rearrangements consisted of increases in ring formations and a more dispersed appearance of the filaments. These results indicate that there is a connection between a dysfunction of nicotine Ca(2+) signaling in

  8. Mapping Lateral Pn Attenuation Variation in Asia

    NASA Astrophysics Data System (ADS)

    Yang, X.; Phillips, W. S.; Randall, G. E.

    2009-12-01

    Pn travels most of its path in the uppermost mantle. Mapping of the lateral variation of Pn amplitude attenuation may shed light on the physical and chemical state, and dynamics of the upper mantle. In addition to material attenuation, Pn amplitudes are affected by other factors including the spherical shape of the Earth and Moho topography. In order to derive reliable Pn attenuation, we adopt a frequency-dependent Pn geometric-spreading model, which was designed to account for the effect of the Earth’s sphericity, to correct Pn amplitudes in preparation for attenuation estimation. We obtain physically reasonable attenuation estimates from Pn amplitudes corrected using the new spreading model. Pn amplitudes corrected using the traditional frequency-independent power-law spreading model, on the other hand, yield attenuation estimates that are either too large or negative. Using properly geometric-spreading corrected Pn amplitudes, we conducted attenuation tomography and developed 2D Pn attenuation models at multiple frequencies from 0.5 Hz to 8 Hz for Asia. Overall Pn attenuation patterns correlate, to some degree, with our current knowledge of the state of the upper mantle of the region. We see consistent low attenuation in cratonic regions and high attenuation along the western Pacific Ocean. The attenuation pattern in the Tibetan Plateau region seems to be frequency dependent with high attenuation around 1 Hz and low attenuation at 8 Hz. Application of the attenuation model to the nuclear-explosion discrimination problem leads to appreciable improvements of the discriminant compared with currently adopted method.

  9. Global survey of frequency dependent attenuation

    NASA Astrophysics Data System (ADS)

    McNamara, D. E.; Benz, H.; Gee, L. S.; Frankel, A. D.

    2011-12-01

    We analyze frequency-dependent attenuation of Lg waves, 1/Q(f), for numerous tectonic environments. Tectonic environments studied include: south Pacific oceanic subduction zone near Samoa, the oblique subduction zone off Hispaniola, two continental-oceanic subduction zones in Chile and Alaska, the continental-continental collision zone of the Tibetan Plateau, stable continental interior regions of the central US and Colorado Plateau, the eastern US passive margin and the active margins of the western US. Lg propagates with a group velocity of about 3.5 km/s, the average crustal shear wave velocity. This wave is commonly observed as the dominant phase on high-frequency seismograms at regional distances and is generated by a superposition of higher-mode surface waves or multiply-reflected shear energy in a crustal waveguide. Consequently, Lg provides a good measure of path-averaged crustal properties, such as shear-wave velocity and attenuation. Lg is particularly useful since its amplitude is sensitive to lateral heterogeneity in the crust due to varying tectonic environment. In this global survey we observe that Lg attenuation is generally higher for tectonically active regions than for stable continental interiors. Q(f) is an important physical parameter and is required for a variety of USGS research projects such as the simulation of strong ground motion and seismic network magnitude detection threshold modeling.

  10. Investigation of guided wave propagation and attenuation in pipe buried in sand

    NASA Astrophysics Data System (ADS)

    Leinov, Eli; Lowe, Michael J. S.; Cawley, Peter

    2015-07-01

    Long-range guided wave testing is a well-established method for detection of corrosion defects in pipelines. The method is currently used routinely for above ground pipelines in a variety of industries, e.g. petrochemical and energy. When the method is applied to pipes buried in soil, test ranges tend to be significantly compromised and unpredictable due to attenuation of the guided wave resulting from energy leakage into the embedding soil. The attenuation characteristics of guided wave propagation in an 8 in. pipe buried in sand are investigated using a laboratory full-scale experimental rig and model predictions. We report measurements of attenuation of the T(0,1) and L(0,2) guided wave modes over a range of sand conditions, including loose, compacted, mechanically compacted, water saturated and drained. Attenuation values are found to be in the range of 1.65-5.5 dB/m and 0.98-3.2 dB/m for the torsional and longitudinal modes, respectively, over the frequency of 11-34 kHz. The application of overburden pressure modifies the compaction of the sand and increases the attenuation. Mechanical compaction of the sand yields similar attenuation values to those obtained with applied overburden pressure. The attenuation decreases in the fully water-saturated sand, and increases in drained sand to values comparable with those obtained for compacted sand. Attenuation measurements are compared with Disperse software model predictions and confirm that the attenuation phenomenon in buried pipes is essentially governed by the bulk shear velocity in the sand. The attenuation behaviour of the torsional guided wave mode is found not to be captured by a uniform soil model; comparison with predictions obtained with the Disperse software suggest that this is likely to be due to a layer of sand adhering to the surface of the pipe.

  11. Attenuated natural killer (NK) cell activation through C-type lectin-like receptor NKp80 is due to an anomalous hemi-immunoreceptor tyrosine-based activation motif (HemITAM) with impaired Syk kinase recruitment capacity.

    PubMed

    Rückrich, Thomas; Steinle, Alexander

    2013-06-14

    Cellular cytotoxicity is the hallmark of NK cells mediating both elimination of virus-infected or malignant cells, and modulation of immune responses. NK cytotoxicity is triggered upon ligation of various activating NK cell receptors. Among these is the C-type lectin-like receptor NKp80 which is encoded in the human Natural Killer Gene Complex (NKC) adjacent to its ligand, activation-induced C-type lectin (AICL). NKp80-AICL interaction promotes cytolysis of malignant myeloid cells, but also stimulates the mutual crosstalk between NK cells and monocytes. While many activating NK cell receptors pair with ITAM-bearing adaptors, we recently reported that NKp80 signals via a hemITAM-like sequence in its cytoplasmic domain. Here we molecularly dissect the NKp80 hemITAM and demonstrate that two non-consensus amino acids, in particular arginine 6, critically impair both hemITAM phosphorylation and Syk recruitment. Impaired Syk recruitment results in a substantial attenuation of cytotoxic responses upon NKp80 ligation. Reconstituting the hemITAM consensus or Syk overexpression resulted in robust NKp80-mediated responsiveness. Collectively, our data provide a molecular rationale for the restrained activation potential of NKp80 and illustrate how subtle alterations in signaling motifs determine subsequent cellular responses. They also suggest that non-consensus alterations in the NKp80 hemITAM, as commonly present among mammalian NKp80 sequences, may have evolved to dampen NKp80-mediated cytotoxic responses toward AICL-expressing cells.

  12. 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.

  13. 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.

  14. Photoacoustic computed tomography correcting for heterogeneity and attenuation

    PubMed Central

    Huang, Chao; Nie, Liming; Schoonover, Robert W.

    2012-01-01

    Abstract. We report an investigation of image reconstruction in photoacoustic tomography for objects that possess heterogeneous material and acoustic attenuation distributions. When the object contains materials, such as bone and soft-tissue, that are modeled using power law attenuation models with distinct exponents, we demonstrate that the effects of acoustic attenuation due to the most strongly attenuating material can be compensated for if the attenuation of the other less attenuating material(s) are neglected. Experiments with phantom objects are presented to validated our findings. PMID:22734741

  15. X-Ray Attenuation Cell

    SciTech Connect

    Ryutov, D.; Toor, A.

    2000-03-03

    To minimize the pulse-to-pulse variation, the LCLS FEL must operate at saturation, i.e. 10 orders of magnitude brighter spectral brilliance than 3rd-generation light sources. At this intensity, ultra-high vacuums and windowless transport are required. Many of the experiments, however, will need to be conducted at a much lower intensity thereby requiring a reliable means to reduce the x-ray intensity by many orders of magnitude without increasing the pulse-to-pulse variation. In this report we consider a possible solution for controlled attenuation of the LCLS x-ray radiation. We suggest using for this purpose a windowless gas-filled cell with the differential pumping. Although this scheme is easily realizable in principle, it has to be demonstrated that the attenuator can be made short enough to be practical and that the gas loads delivered to the vacuum line of sight (LOS) are acceptable. We are not going to present a final, optimized design. Instead, we will provide a preliminary analysis showing that the whole concept is robust and is worth further study. The spatial structure of the LCLS x-ray pulse at the location of the attenuator is shown in Fig. 1. The central high-intensity component, due to the FEL, has a FWHM of {approx}100 {micro}m. A second component, due to the undulator's broad band spontaneous radiation is seen as a much lower intensity ''halo'' with a FWHM of 1 mm. We discuss two versions of the attenuation cell. The first is directed towards a controlled attenuation of the FEL up to the 4 orders of magnitude in the intensity, with the spontaneous radiation halo being eliminated by collimators. In the second version, the spontaneous radiation is not sacrificed but the FEL component (as well as the first harmonic of the spontaneous radiation) gets attenuated by a more modest factor up to 100. We will make all the estimates assuming that the gas used in the attenuator is Xenon and that the energy of the FEL is 8.25 keV. At lower FEL energies the

  16. Reduced difference of α₂-plasmin inhibitor levels between plasma and serum in patients with severe factor XIII deficiency, including autoimmune hemorrhaphilia due to anti-factor XIII antibodies.

    PubMed

    Ichinose, Akitada; Souri, Masayoshi

    2012-01-01

    Coagulation factor XIII/13 (FXIII/13) stabilizes fibrin molecules by creating crosslinks with other fibrin molecules as well as with α₂-plasmin inhibitor (α₂-PI). "Hemorrhagic acquired FXIII/13 deficiency" was formerly considered rare, but has been increasing recently in Japan. During the 10 months of our nationwide campaign, we diagnosed five new patients with "acquired hemorrhaphilia due to anti-FXIII/13 autoantibodies," after examining 20 newly suspected cases of "hemorrhagic acquired FXIII/13 deficiency." When FXIII/13 activity was reduced to less than 50% of normal, it was proportional to the difference in α₂-PI levels between plasma and serum (plasma-serum α₂-PI), likely due to its cross-linking to fibrin by activated FXIII/13. Accordingly, decreased amounts of the plasma-serum α₂-PI ex vivo may reflect reduced FXIII/13 activity in vivo. The plasma-serum α₂-PI may thus also be a useful diagnostic marker for severe FXIII/13 deficiency.

  17. 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.

  18. 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

  19. Dividing of Q factor of viscous and intrinsic attenuation in poroelastic media

    NASA Astrophysics Data System (ADS)

    Ishikura, K.; Mikada, H.; Goto, T.; Takekawa, J.

    2013-12-01

    Sonic logging has been widely used for many years to understand physical properties of hydrocarbon reservoirs. When gaseous phase exists in the formation fluid, the compressional waves traveling through the formation could be strongly attenuated due to low bulk modulus of gas in the fluid, while the shear waves are not. For acquiring physical properties of fluid in the formation, Biot physics or poroelastic analysis could be the best method. Among the available technologies, quality factors based on the Biot's equation could be used. Although the Biot's theory considers the viscous attenuation induced at the interface between rocks and pore fluids, the intrinsic attenuation caused by the internal friction in the matrix is ignored. In the present study, we investigate how large are the effects of the intrinsic attenuation of compressional waves through the evaluation of the reservoir properties based on the quality factor. We employ a 2D finite-difference scheme to simulate seismic wave propagation in a poroelasic medium. The intrinsic attenuation is included in our model by using the filter of frequency-independent quality factor (constant-Q). We then compare the results compressional waves and shear waves with the intrinsic attenuation in our numerical simulations. Our results clearly show that on compressional and shear waves, the amplitude and phase of the waveforms are strongly affected by the intrinsic attenuation, and we could get only the viscous attenuation by the results of quality factor of compressional wave and shear wave. We conclude that the evaluations of hydrocarbon reservoir require the consideration of the intrinsic attenuation as well as the viscous attenuation predicted by the Biot's theory and also we could get what kind of fluid is contained in the reservoir. The profile of Q factor

  20. THE NATIONAL RESEARCH COUNCIL REPORT ON MONITORED NATURAL ATTENUATION

    EPA Science Inventory

    The National Research Council recently released a report titled Natural Attenuation for Groundwater Remediation, available from the National Academy Press(http://www.nap.edu>). The report made a number of observations and recommedations, including the following. -Natural attenu...

  1. THE NATIONAL RESEARCH COUNCIL REPORT ON MONITORED NATURAL ATTENUATION

    EPA Science Inventory

    The National Research Council recently released a report titled Natural Attenuation for Groundwater Remediation, available from the National Academy Press(http://www.nap.edu>). The report made a number of observations and recommedations, including the following. -Natural attenu...

  2. Multiple tumor types including leiomyoma and Wilms tumor in a patient with Gorlin syndrome due to 9q22.3 microdeletion encompassing the PTCH1 and FANC-C loci.

    PubMed

    Garavelli, Livia; Piemontese, Maria Rosaria; Cavazza, Alberto; Rosato, Simonetta; Wischmeijer, Anita; Gelmini, Chiara; Albertini, Enrico; Albertini, Giuseppe; Forzano, Francesca; Franchi, Fabrizia; Carella, Massimo; Zelante, Leopoldo; Superti-Furga, Andrea

    2013-11-01

    Gorlin syndrome or nevoid basal cell carcinoma syndrome (NBCCS) is an autosomal dominant condition mainly characterized by the development of mandibular keratocysts which often have their onset during the second decade of life and/or multiple basal cell carcinoma (BCC) normally arising during the third decade. Cardiac and ovarian fibromas can be found. Patients with NBCCS develop the childhood brain malignancy medulloblastoma (now often called primitive neuro-ectodermal tumor [PNET]) in 5% of cases. The risk of other malignant neoplasms is not clearly increased, although lymphoma and meningioma can occur in this condition. Wilms tumor has been mentioned in the literature four times. We describe a patient with a 10.9 Mb 9q22.3 deletion spanning 9q22.2 through 9q31.1 that includes the entire codifying sequence of the gene PTCH1, with Wilms tumor, multiple neoplasms (lung, liver, mesenteric, gastric and renal leiomyomas, lung typical carcinoid tumor, adenomatoid tumor of the pleura) and a severe clinical presentation. We propose including leiomyomas among minor criteria of the NBCCS.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. The LCLS Gas Attenuator Revisited

    SciTech Connect

    Ryutov, D

    2005-06-07

    In the report ''X-ray attenuation cell'' [1] a preliminary analysis of the gas attenuator for the Linac Coherent Light Source (LCLS) was presented. This analysis was carried out for extremely stringent set of specifications. In particular, a very large diameter for the unobstructed beam was set (1 cm) to accommodate the spontaneous radiation; the attenuator was supposed to cover the whole range of energies of the coherent radiation, from 800 eV to 8000 eV; the maximum attenuation was set at the level of 10{sup 4}; the use of solid attenuators was not allowed, as well as the use of rotating shutters. The need to reach a sufficient absorption at the high-energy end of the spectrum predetermined the choice of Xe as the working gas (in order to have a reasonable absorption at a not-too-high pressure). A sophisticated differential pumping system that included a Penning-type ion pump was suggested in order to minimize the gas leak into the undulator/accelerator part of the facility. A high cost of xenon meant also that an efficient (and expensive) gas-recovery system would have to be installed. The main parameter that determined the high cost and the complexity of the system was a large radius of the orifice. The present viewpoint allows for much smaller size of the orifice, r{sub 0} = 1.5 mm. (1) The use of solid attenuators is also allowed (R.M. Bionta, private communication). It is, therefore, worthwhile to reconsider various parameters of the gas attenuator for these much less stringent conditions. This brief study should be considered as a physics input for the engineering design. As a working gas we consider now the argon, which, on the one hand, provides a reasonable absorption lengths and, on the other hand, is inexpensive enough to be exhausted into the atmosphere (no recovery). The absorption properties of argon are illustrated by Fig.1 where the attenuation factor A is shown for various beam energies, based on Ref. [2]. The other relevant parameters for argon

  8. Gaining Regulator Acceptance of Natural Attenuation as a Remediation Tool

    SciTech Connect

    Hughes, M.B.

    2001-01-29

    Monitored natural attenuation (MNA) makes use of biological degradation, chemical reactions with natural materials, and other processes to clean up contaminated soils and groundwater. In the past, the regulatory community has been slow to accept natural attenuation due to a misperception that natural attenuation is a ''do nothing'' approach. Recently however, regulators have been more open to considering MNA as part of an overall clean-up plan that includes active treatment technologies to remove or contain the source of contamination at a site. MNA is currently being implemented at the Savannah River Site for remediation of selected contaminants. The South Carolina Department of Health and Environmental Control, who has regulatory authority over these actions, has accepted this process. Significant overall cost savings are forecast. Additionally, there will be less disruption to the ecosystem, compared with engineered technologies. This paper describes the monitored natural attenuation concept as well as the process of constructive engagement with the regulators to achieve acceptance. Application to DOE, DOD, and commercial sites, as well as acceptability to other regulatory bodies, will be discussed with an emphasis on strategies to prevent false starts in the negotiation process and inventing options that result in mutual gains for all parties.

  9. 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...

  10. 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...

  11. 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.

  12. 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.

  13. Transcription attenuation in bacteria: theme and variations.

    PubMed

    Naville, Magali; Gautheret, Daniel

    2009-11-01

    Premature termination of transcription, or attenuation, is an efficient RNA-based regulatory strategy that is commonly used in bacterial organisms. Attenuators are generally located in the 5' untranslated regions of genes or operons and combine a Rho-independent terminator, controlling transcription, with an RNA element that senses specific environmental signals. A striking diversity of sensing elements enable regulation of gene expression in response to multiple environmental conditions, including temperature changes, availability of small metabolites (such as ions, amino acids, nucleobases or vitamins), or availability of macromolecules such as tRNAs and regulatory proteins. The wide distribution of attenuators suggests an early emergence among bacteria. However, attenuators also display a great mobility and lability, illustrated by a multiplicity of recent horizontal transfers and duplications. For these reasons, attenuation systems are of high interest both from a fundamental evolutionary perspective and for possible biotechnological applications.

  14. Transcription attenuation in bacteria: theme and variations.

    PubMed

    Naville, Magali; Gautheret, Danie

    2010-03-01

    Premature termination of transcription, or attenuation, is an efficient RNA-based regulatory strategy that is commonly used in bacterial organisms. Attenuators are generally located in the 50 untranslated regions of genes or operons and combine a Rho-independent terminator, controlling transcription, with an RNA element that senses specific environmental signals. A striking diversity of sensing elements enable regulation of gene expression in response to multiple environmental conditions, including temperature changes, availability of small metabolites(such as ions, amino acids, nucleobases or vitamins), or availability of macromolecules such as tRNAs and regulatory proteins. The wide distribution of attenuators suggests an early emergence among bacteria. However, attenuators also display a great mobility and lability, illustrated by a multiplicity of recent horizontal transfers and duplications.For these reasons, attenuation systems are of high interest both from a fundamental evolutionary perspective and for possible biotechnological applications.

  15. Attenuation of landfill leachate by clay liner materials in laboratory columns: 2. Behaviour of inorganic contaminants.

    PubMed

    Thornton, S F; Lerner, D N; Tellam, J H

    2001-02-01

    The chemical attenuation of inorganic contaminants in methanogenic landfill leachate, spiked with heavy metals (Cd, Cd, Ni and Zn), by two UK clay liner materials was compared in laboratory columns over 15 months. Ammonium was attenuated by ion-exchange but this attenuation was finite and when exhausted, NH4 passed through the liners at concentrations found in the leachate. The breakthrough behaviour of NH4 could be described by a simple distribution coefficient. Heavy metals were attenuated by sorption and precipitation of metal sulphide and carbonate compounds near the top of the liner. Adequate SO4 and CaCO3 in the liner is necessary to ensure the long term retention of heavy metals, and pH buffering agents added to stabilise reactive metal fractions should be admixed with the liner. Some metals may not be chemically attenuated by clay liners due to the formation of stable complexes with organic and/or colloidal fractions in leachate. Flushing of the liners with oxygenated water after leachate caused mobilisation of attenuated contaminants. Sorbed NH4 was released by the liners but groundwater loadings were manageable. Re-oxidation of metal sulphides under these conditions resulted in the release of heavy metals from the liners when the pH buffering capacity was poor. Contaminant attenuation by the clay liners was similar and the attenuation of NH4 and heavy metals could be predicted from the geochemical properties of the liner using simple tests. A conceptual model of clay liner performance is presented. Chemical attenuation of inorganic pollutants can be included in containment liner design to produce a dual reactive-passive barrier for landfills.

  16. 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.

  17. 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.

  18. 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.

  19. 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)

  20. 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.

  1. 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.

  2. Contaminant attenuation by shallow aquifer systems under steady flow

    NASA Astrophysics Data System (ADS)

    Soltani, S. S.; Cvetkovic, V.

    2017-10-01

    We present a framework for analyzing advection-dominated solute transport and transformation in aquifer systems of boreal catchments that are typically shallow and rest on crystalline bedrock. A methodology is presented for estimating tracer discharge based on particle trajectories from recharge to discharge locations and computing their first passage times assuming that the flow pattern is approximately steady-state. Transformation processes can be included by solving one-dimensional reactive transport with randomized water travel time as the independent variable; the distribution of the travel times incorporates morphological dispersion (due to catchment geometry/topography) as well as macro-dispersion (due to heterogeneity of underlying hydraulic properties). The implementation of the framework is illustrated for the well characterized coastal catchment of Forsmark (Sweden). We find that macro-dispersion has a notable effect on attenuation even though the morphological dispersion is significantly larger. Preferential flow on the catchment scale is found to be considerable with only 5% of the Eulerian velocities contributing to transport over the simulation period of 375 years. Natural attenuation is illustrated as a simple (linear decay) transformation process. Simulated natural attenuation can be estimated analytically reasonably well by using basic hydrological and structural information, the latter being the pathway length distribution and average aquifer depth to the bedrock.

  3. Attenuation Modified by DIG and Dust as Seen in M31

    NASA Astrophysics Data System (ADS)

    Tomičić, Neven; Kreckel, Kathryn; Groves, Brent; Schinnerer, Eva; Sandstrom, Karin; Kapala, Maria; Blanc, Guillermo A.; Leroy, Adam

    2017-08-01

    The spatial distribution of dust in galaxies affects the global attenuation, and hence inferred properties, of galaxies. We trace the spatial distribution of dust in five approximately kiloparsec fields of M31 by comparing optical attenuation with the total dust mass distribution. We measure the attenuation from the Balmer decrement using Integral Field Spectroscopy and the dust mass from Herschel far-IR observations. Our results show that M31's dust attenuation closely follows a foreground screen model, contrary to what was previously found in other nearby galaxies. By smoothing the M31 data, we find that spatial resolution is not the cause for this difference. Based on the emission-line ratios and two simple models, we conclude that previous models of dust/gas geometry need to include a weakly or non-attenuated diffuse ionized gas (DIG) component. Due to the variation of dust and DIG scale heights with galactic radius, we conclude that different locations in galaxies will have different vertical distributions of gas and dust and therefore different measured attenuation. The difference between our result in M31 with that found in other nearby galaxies can be explained by our fields in M31 lying at larger galactic radii than the previous studies that focused on the centers of galaxies.

  4. Comparison of Reg. Guide 1.99 fluence attenuation methods

    SciTech Connect

    Jones, E.N.

    2011-07-01

    U.S. Regulatory Guide 1.99 Revision 2 (U.S. Nuclear Regulatory Commission, 1988, 'Radiation Embrittlement of Reactor Vessel Materials,' Regulatory Guide 1.99, Revision 2, Washington, D.C.) provides for the use of two substantially different methods for determining through-wall fluence in nuclear reactor pressure vessels. One method is a generic attenuation curve based on a simplistic exponential decay equation. Partly due to the simplicity of its application, the generic attenuation method is predominantly used for licensing calculations. However, it has a limitation in that at increasing distances away from the core belt-line, it becomes increasingly less accurate because it cannot account for neutron streaming effects in the cavity region surrounding the pressure vessel. The other attenuation method is based on a displacement per atom (dpa) calculation specific to the reactor vessel structure. The dpa method provides a more accurate representation of fluence attenuation through the reactor pressure vessel (RPV) wall at all elevations of the pressure vessel because it does account for neutron streaming in the cavity region. A requirement for using the dpa method, however, is an accurate flux solution through the RPV wall. This requirement has limited the use of traditional transport methods, such as discrete ordinates, that are limited by their treatment of cavity regions (i.e., air) outside the pressure vessel wall. TransWare Enterprises, under the sponsorship of EPRI and BWRVIR has developed an advanced three-dimensional transport methodology capable of producing fully converged flux solutions throughout the entire reactor system, including in the cavity region and primary shield structures. This methodology provides an accurate and reliable determination of through-wall fluence in boiling water reactor (BWR) and pressurized water reactor (PWR) pressure vessels, thus allowing the dpa method to be implemented with high reliability. Using this advanced 3-D

  5. 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.

  6. 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)

  7. 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.

  8. Live attenuated vaccines for invasive Salmonella infections

    PubMed Central

    Tennant, Sharon M.; Levine, Myron M.

    2015-01-01

    Salmonella enterica serovar Typhi produces significant morbidity and mortality worldwide despite the fact that there are licensed S. 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: S. Typhi, S. Paratyphi A, S. Paratyphi B (currently uncommon but may become dominant again), S. Typhimurium, S. Enteritidis and S. 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

  9. 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

  10. Role of intertidal wetlands for tidal and storm tide attenuation along a confined estuary: a model study

    NASA Astrophysics Data System (ADS)

    Smolders, S.; Plancke, Y.; Ides, S.; Meire, P.; Temmerman, S.

    2015-07-01

    Coastal lowlands and estuaries are subjected to increasing flood risks during storm surges due to global and regional changes. Tidal wetlands are increasingly valued as effective natural buffers for storm surges by dissipating wave energy and providing flood water storage. While previous studies focused on flood wave attenuation within and behind wetlands, this study focuses on the effects of estuarine wetland properties on the attenuation of a storm tide that propagates along the length of an estuary. Wetland properties including elevation, surface area, and location within the estuary were investigated using a numerical model of the Scheldt estuary (Belgium, SW Netherlands). For a spring tide lower wetland elevations result in more attenuation of high water levels along the estuary, while for a higher storm tide higher elevations provide more attenuation compared to lower wetland elevations. For spring and storm tide a larger wetland surface area results in a better attenuation along the estuary up to a threshold wetland size for which larger wetlands do not further contribute to more attenuation. Finally a wetland of the same size and elevation, but located more upstream in the estuary, can store a larger proportion of the local flood volume and therefore has a larger attenuating effect on upstream high water levels. With this paper we aim to contribute towards a better understanding and wider implementation of ecosystem-based adaptation to increasing estuarine flood risks associated with storms.

  11. Role of intertidal wetlands for tidal and storm tide attenuation along a confined estuary: a model study

    NASA Astrophysics Data System (ADS)

    Smolders, S.; Plancke, Y.; Ides, S.; Meire, P.; Temmerman, S.

    2015-05-01

    Coastal lowlands and estuaries are subjected to increasing flood risks during storm surges due to global and regional changes. Tidal wetlands are increasingly valued as effective natural buffers for storm surges by dissipating wave energy and providing flood water storage. While previous studies focused on flood wave attenuation within and behind wetlands, this study focuses on the effects of estuarine wetland properties on the attenuation of a storm tide that propagates along the length of an estuary. Wetland properties including elevation, surface area, and location within the estuary were investigated using a numerical model of the Scheldt estuary (Belgium, SW Netherlands). For a spring tide lower wetland elevations result in more attenuation of high water levels along the estuary, while for a higher storm tide higher elevations provide more attenuation compared to lower wetland elevations. For spring and storm tide a arger wetland surface area results in a better attenuation along the estuary up to a threshold wetland size for which larger wetlands do not further contribute to more attenuation. Finally a wetland of the same size and elevation, but located more upstream in the estuary, can store a larger proportion of the local flood volume and therefore has a larger attenuating effect on upstream high water levels. With this paper we aim to contribute towards a better understanding and wider implementation of ecosystem-based adaptation to increasing estuarine flood risks associated with storms.

  12. Magnetoelectric Composite Based Microwave Attenuator

    NASA Astrophysics Data System (ADS)

    Tatarenko, A. S.; Srinivasan, G.

    2005-03-01

    Ferrite-ferroelectric composites are magnetoelectric (ME) due to their response to elastic and electromagnetic force fields. The ME composites are characterized by tensor permittivity, permeability and ME susceptibility. The unique combination of magnetic, electrical, and ME interactions, therefore, opens up the possibility of electric field tunable ferromagnetic resonance (FMR) based devices [1]. Here we discuss an ME attenuator operating at 9.3 GHz based on FMR in a layered sample consisting of lead magnesium niobate-lead titanate bonded to yttrium iron garnet (YIG) film on a gadolinium gallium garnet substrate. Electrical tuning is realized with the application of a control voltage due to ME effect; the shift is 0-15 Oe as E is increased from 0 to 3 kV/cm. If the attenuator is operated at FMR, the corresponding insertion loss will range from 25 dB to 2 dB. 1. S. Shastry and G. Srinivasan, M.I. Bichurin, V.M. Petrov, A.S. Tatarenko. Phys. Rev. B, 70 064416 (2004). - supported by grants the grants from the National Science Foundation (DMR-0302254), from Russian Ministry of Education (Å02-3.4-278) and from Universities of Russia Foundation (UNR 01.01.026).

  13. Response attenuation during coincident afferent excitatory inputs.

    PubMed

    Kogo, N; Ariel, M

    1999-06-01

    The linearity of the synaptic summation of two unitary excitatory synaptic events was investigated during whole cell recordings from retinal target neurons in an eye-attached isolated brain stem preparation. Pairs of unitary excitatory postsynaptic potentials (EPSPs) were evoked by bipolar stimulation electrodes that were directed to two distinct foci on the retinal surface based on the visual receptive field boundaries. The interval between stimulation of each retinal site was incremented by 0.5-1 ms to quantify the time course of nonlinear summation using an exponential fit. Response facilitation was never observed; however, the coincident arrival of synaptic inputs caused a response attenuation in 26 of the 37 pairs studied. Twelve of the 26 pairs had time constants of their attenuation that were similar to the time constants of the decaying phases of the first EPSPs of each pair. This suggests that the attenuation of these 12 pairs may be entirely due to voltage-dependent mechanisms, such as a reduction in driving force or a change of the activity of voltage-sensitive channels. On the other hand, the 14 other pairs had their time constant of attenuation shorter than the time constants of the decaying phase of the first EPSP. In fact, the attenuation time constants were often closer to the time constants of the decaying phases of the first excitatory postsynaptic currents of each pair. This finding suggests that the attenuation of these 14 pairs involve a shunting mechanism due to the opening of synaptic channels. The presence of this conductance-dependent mechanism is supported by the finding of asymmetric effects on the time course of attenuation when the stimulation sequence was reversed. These results are discussed in terms of the processing by neurons of coincident excitatory inputs onto spatially distinct points of their dendritic trees.

  14. Vortex attenuation flight experiments

    NASA Technical Reports Server (NTRS)

    Barber, M. R.; Hastings, E. C., Jr.; Champine, R. A.; Tymczyszyn, J. J.

    1977-01-01

    Flight tests evaluating the effects of altered span loading, turbulence ingestion, combinations of mass and turbulence ingestion, and combinations of altered span loading turbulance ingestion on trailed wake vortex attenuation were conducted. Span loadings were altered in flight by varying the deflections of the inboard and outboard flaps on a B-747 aircraft. Turbulence ingestion was achieved in flight by mounting splines on a C-54G aircraft. Mass and turbulence ingestion was achieved in flight by varying the thrust on the B-747 aircraft. Combinations of altered span loading and turbulence ingestion were achieved in flight by installing a spoiler on a CV-990 aircraft and by deflecting the existing spoilers on a B-747 aircraft. The characteristics of the attenuated and unattenuated vortexes were determined by probing them with smaller aircraft. Acceptable separation distances for encounters with the attenuated and unattenuated vortexes are presented.

  15. Ultrasound attenuation in ferrofluids.

    PubMed

    Shliomis, Mark; Mond, Michael; Morozov, Konstantin

    2008-08-15

    The absorption of acoustic energy by internal degrees of freedom of short chains is proposed as a new viable mechanism of ultrasound attenuation in ferrofluids. It is demonstrated that even though the volume fraction of the chains may be quite small, such an effect may reach the order of magnitude of viscous damping. In addition, by investigating the statistical properties of dimers in ferrofluids, it is shown that an applied magnetic field modifies the sound attenuation in a highly anisotropic manner. The proposed mechanism provides new insight into the fundamental issue of colloidal response, and, in particular, may lead to its utilization in novel experimental concepts.

  16. 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.

  17. 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.

  18. 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.

  19. Attenuation tomography in West Bohemia/Vogtland

    NASA Astrophysics Data System (ADS)

    Mousavi, Sima; Haberland, Christian; Bauer, Klaus; Hejrani, Babak; Korn, Michael

    2017-01-01

    We present a three-dimensional (3-D) P-wave attenuation (Qp) model for the geodynamically active swarm earthquake area of West Bohemia/Vogtland in the Czech/German border region. Path-averaged attenuation t* is calculated from amplitude spectra of time windows around the P-wave arrivals of local earthquakes. Average t/t* value or Qp for stations close to Nový Kostel are very low (< 150) compared to that of stations located further away from the focal zone (increases up to 500 within 80 km distance). The SIMUL2000 tomography scheme is used to invert the t* for P-wave attenuation perturbation. Analysis of resolution shows that our model is well-resolved in the vicinity of earthquake swarm hypocenters. The prominent features of the model are located around Nový Kostel focal zone and its northern vicinity. Beneath Nový Kostel a vertically stretched (down to depth of 11 km) and a highly attenuating body is observed. We believe that this is due to fracturing and high density of cracks inside the weak earthquake swarm zone in conjunction with presence of free gas/fluid. Further north of Nový Kostel two highly attenuating bodies are imaged which could represent fluid channels toward the surface. The eastern anomaly shows a good correlation with the fluid accumulation area which was suggested in 9HR seismic profile.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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 WITH...

  5. 34 CFR 303.15 - Include; including.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 34 Education 2 2011-07-01 2010-07-01 true 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 WITH...

  6. Problems created in attenuation-corrected SPECT images by artifacts in attenuation maps: a simulation study.

    PubMed

    Celler, Anna; Dixon, Katherine L; Chang, Zheng; Blinder, Stephan; Powe, John; Harrop, Ronald

    2005-02-01

    The importance of accurate attenuation correction, especially for imaging of the thorax region, is widely acknowledged. Appropriate compensation methods have been developed and introduced into clinical practice. Most of these methods use attenuation maps obtained using various transmission scanning systems. However, when maps are inaccurate, the correction procedure may introduce artifacts into the final images that can be difficult to identify and might inadvertently alter diagnosis and study outcome. As a result, attenuation correction is often avoided in clinical practice. Our objective was to examine issues related to the quality of attenuation maps and the effects that map artifacts may have on attenuation-corrected emission images. The topics that are investigated include the problem of low transmission counts, cross-talk contributions from the emission isotope, truncation of the transmission data, and methods of map reconstruction and segmentation. Examples of patient studies displaying specific problems guided our investigations, but, because truth in these studies is seldom known, analytic and Monte Carlo-simulated data were used in the analysis. Attenuation maps and final emission images were visually checked for artifacts and for the presence of perfusion defects. In addition, quantitative evaluation of map uniformity, defect visibility, and size variation was performed. The statistical paired-sample t test showed significant (P < 0.05) improvement of relative SD for attenuation maps reconstructed with iterative methods as compared with filtered backprojection and for maps created with higher photon fluxes. When maps with artifacts were used to correct emission data, an increase in myocardial infarct size and creation of false heart defects were observed. Our study strongly recommends that at least a visual inspection of the quality of attenuation maps be performed before their use in compensation procedures. To improve image quality, remove artifacts

  7. Validation of attenuation, beam blockage, and calibration estimation methods using two dual polarization X band weather radars

    NASA Astrophysics Data System (ADS)

    Diederich, M.; Ryzhkov, A.; Simmer, C.; Mühlbauer, K.

    2011-12-01

    The amplitude a of radar wave reflected by meteorological targets can be misjudged due to several factors. At X band wavelength, attenuation of the radar beam by hydro meteors reduces the signal strength enough to be a significant source of error for quantitative precipitation estimation. Depending on the surrounding orography, the radar beam may be partially blocked when scanning at low elevation angles, and the knowledge of the exact amount of signal loss through beam blockage becomes necessary. The phase shift between the radar signals at horizontal and vertical polarizations is affected by the hydrometeors that the beam travels through, but remains unaffected by variations in signal strength. This has allowed for several ways of compensating for the attenuation of the signal, and for consistency checks between these variables. In this study, we make use of several weather radars and gauge network measuring in the same area to examine the effectiveness of several methods of attenuation and beam blockage corrections. The methods include consistency checks of radar reflectivity and specific differential phase, calculation of beam blockage using a topography map, estimating attenuation using differential propagation phase, and the ZPHI method proposed by Testud et al. in 2000. Results show the high effectiveness of differential phase in estimating attenuation, and potential of the ZPHI method to compensate attenuation, beam blockage, and calibration errors.

  8. On the estimation of risk associated with an attenuation prediction

    NASA Technical Reports Server (NTRS)

    Crane, R. K.

    1992-01-01

    Viewgraphs from a presentation on the estimation of risk associated with an attenuation prediction is presented. Topics covered include: link failure - attenuation exceeding a specified threshold for a specified time interval or intervals; risk - the probability of one or more failures during the lifetime of the link or during a specified accounting interval; the problem - modeling the probability of attenuation by rainfall to provide a prediction of the attenuation threshold for a specified risk; and an accounting for the inadequacy of a model or models.

  9. 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

  10. Control algorithms for dynamic attenuators

    PubMed Central

    Hsieh, Scott S.; Pelc, Norbert J.

    2014-01-01

    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 require a 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

  11. Attenuation Tomography in Eastern Russia

    NASA Astrophysics Data System (ADS)

    Rowe, C. A.; Phillips, W. S.; Hartse, H. E.; Steck, L. K.; Begnaud, M. L.; Mackey, K. G.; Fujita, K.

    2006-12-01

    We are using catalog amplitude parameters to derive a 2D function that maps laterally-varying attenuation features for eastern Siberia and the Russian Far East. Our information is from the Michigan State University (MSU) Siberia database, compiled through cooperative efforts of MSU, Russian network operators and Los Alamos researchers. The database also includes information from teleseismic bulletins, such as those provided by the International Seismological Centre, U.S. Geological Survey and Alaska Earthquake Information Center. For Siberia we have ~242,000 S and Sg amplitude readings and ~140,000 P and Pg amplitude readings for source-to-receiver distances in the local to regional range (0 to 15 degrees). In Kamchatka, ~155,000 S amplitude measurements and 85,000 P amplitudes are reported. We derive the 2D attenuation mapping using tomographic methods. The results of our inversion will be compared with known tectonic features in northeastern Russia and with velocity perturbation features derived for the region in previous work.

  12. 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.

  13. 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.

  14. Retrodiction for optical attenuators, amplifiers, and detectors

    SciTech Connect

    Jedrkiewicz, Ottavia; Loudon, Rodney; Jeffers, John

    2004-09-01

    The transformation that an attenuator makes on the state of an optical field is the time reverse of that of an amplifier. Thus predicting the output state for an amplifier is equivalent to retrodicting the input state of an attenuator. We explore the consequences of this equivalence for simple optical quantum communication channels. One counterintuitive consequence is that the mean number of photons sent into an amplifier as retrodicted from a measurement of the number of output photons does not include the contribution of the amplifier noi0008.

  15. 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.

  16. Assessment of satellite derived diffuse attenuation coefficients ...

    EPA Pesticide Factsheets

    Optical data collected in coastal waters off South Florida and in the Caribbean Sea between January 2009 and December 2010 were used to evaluate products derived with three bio-optical inversion algorithms applied to MOIDS/Aqua, MODIS/Terra, and SeaWiFS satellite observations. The products included the diffuse attenuation coefficient at 490 nm (Kd_490) and for the visible range (Kd_PAR), and euphotic depth (Zeu, corresponding to 1% of the surface incident photosynthetically available radiation or PAR). Above-water hyperspectral reflectance data collected over optically shallow waters of the Florida Keys between June 1997 and August 2011 were used to help understand algorithm performance over optically shallow waters. The in situ data covered a variety of water types in South Florida and the Caribbean Sea, ranging from deep clear waters, turbid coastal waters, and optically shallow waters (Kd_490 range of ~0.03 – 1.29m-1). An algorithm based on Inherent Optical Properties (IOPs) showed the best performance (RMSD < 13% and R2 ~1.0 for MODIS/Aqua and SeaWiFS). Two algorithms based on empirical regressions performed well for offshore clear waters, but underestimated Kd_490 and Kd_PAR in coastal waters due to high turbidity or shallow bottom contamination. Similar results were obtained when only in situ data were used to evaluate algorithm performance. The excellent agreement between satellite-derived remote sensing reflectance (Rrs) and in situ Rrs suggested that

  17. Sizes of mantle heteogeneities and seismic attenuation

    NASA Astrophysics Data System (ADS)

    Ricard, Y. R.; durand, S.; Chambat, F.; Montagner, J.

    2013-12-01

    The small scale heterogeneity of the mantle, being mostly due to the mixing of petrological heterogeneities by a smooth but chaotic convection 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 spectrums. We show that a seismic wave of wavenumber k_0 crossing such medium is partly reflected by the heterogeneities and the scattered energy has an energy found proportional to k_0 S(2k_0). The reduction of energy for the propagating wave appears therefore equivalent to a quality factor 1/Q proportional to k_0 S(2k_0). 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 there are not unreasonable and we discuss how they are likely overestimated. In this case, most of the attenuation of the Earth would be due to small scale scattering by laminations not by intrinsic dissipation. Intrinsic dissipation must certainly exists but might correspond to a larger, yet unobserved Q. This provocative result would explain the observed very weak frequency dependence of the attenuation, and the fact that bulk attenuation seems negligeable, two observations that have been difficult to explain for 50 years.

  18. Ultrasonic attenuation in molecular crystals

    NASA Astrophysics Data System (ADS)

    Perrin, Bernard

    1981-11-01

    It is now well established from an experimental point of view that, concerning the ultrasonic attenuation, molecular crystals exhibit a specific behavior among dielectric crystals. This fact suggests the presence of a relaxation process. Liebermann, who has introduced this field, has proposed a way to analyze this problem and in particular has given an expression for the ultrasonic absorption coefficient in terms of a relaxation time and some thermodynamic quantities. In contrast to Liebermann's approach, a solid-state viewpoint is presented here, and it is shown that this ultrasonic relaxation can be taken into account in the framework of Akhieser's theory. A general expression of the ultrasonic absorption coefficient is calculated in terms of the phonon collision operator using the Boltzmann-equation approach of Woodruff and Ehrenreich. The collision-time approximation widely used in dielectric crystals fails in molecular crystals for which the presence of slow relaxation times in the collision operator prevents the thermalization of the whole set of phonons and gives rise to an ultrasonic relaxation. Thus a more suitable approximation is suggested here, which leads to a new expression of the ultrasonic attenuation valid in molecular crystals. Different forms of this expression are discussed, and comparison with Liebermann's expression used in most of the previous papers shows that the present treatment takes better account of the anisotropy of the solid state. The fit of experimental results obtained for some ionic-molecular crystals also shows that the expression derived here gives better agreement than does Liebermann's. Finally, it is shown that in the framework of the present treatment and under rather general conditions, the anisotropy affects primarily the magnitude of the ultrasonic absorption due to the molecular relaxation, but it does not affect its frequency dependence.

  19. 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.

  20. 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

  1. 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

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

    2012-02-23

    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.

  2. 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.

  3. Physiological and Perceptual Sensory Attenuation Have Different Underlying Neurophysiological Correlates.

    PubMed

    Palmer, Clare E; Davare, Marco; Kilner, James M

    2016-10-19

    Sensory attenuation, the top-down filtering or gating of afferent information, has been extensively studied in two fields: physiological and perceptual. Physiological sensory attenuation is represented as a decrease in the amplitude of the primary and secondary components of the somatosensory evoked potential (SEP) before and during movement. Perceptual sensory attenuation, described using the analogy of a persons' inability to tickle oneself, is a reduction in the perception of the afferent input of a self-produced tactile sensation due to the central cancellation of the reafferent signal by the efference copy of the motor command to produce the action. The fields investigating these two areas have remained isolated, so the relationship between them is unclear. The current study delivered median nerve stimulation to produce SEPs during a force-matching paradigm (used to quantify perceptual sensory attenuation) in healthy human subjects to determine whether SEP gating correlated with the behavior. Our results revealed that these two forms of attenuation have dissociable neurophysiological correlates and are likely functionally distinct, which has important implications for understanding neurological disorders in which one form of sensory attenuation but not the other is impaired. Time-frequency analyses revealed a negative correlation over sensorimotor cortex between gamma-oscillatory activity and the magnitude of perceptual sensory attenuation. This finding is consistent with the hypothesis that gamma-band power is related to prediction error and that this might underlie perceptual sensory attenuation.

  4. Excess attenuation of an acoustic beam by turbulence.

    PubMed

    Pan, Naixian

    2003-12-01

    A theory based on the concept of a spatial sinusoidal diffraction grating is presented for the estimation of the excess attenuation in an acoustic beam. The equation of the excess attenuation coefficient shows that the excess attenuation of acoustic beam not only depends on the turbulence but also depends on the application parameters such as the beam width, the beam orientation and whether for forward propagation or back scatter propagation. Analysis shows that the excess attenuation appears to have a frequency dependence of cube-root. The expression for the excess attenuation coefficient has been used in the estimations of the temperature structure coefficient, C(T)2, in sodar sounding. The correction of C(T)2 values for excess attenuation reduces their errors greatly. Published profiles of temperature structure coefficient and the velocity structure coefficient in convective conditions are used to test our theory, which is compared with the theory by Brown and Clifford. The excess attenuation due to scattering from turbulence and atmospheric absorption are both taken into account in sodar data processing for deducing the contribution of the lower atmosphere to seeing, which is the sharpness of a telescope image determined by the degree of turbulence in the Earth's atmosphere. The comparison between the contributions of the lowest 300-m layer to seeing with that of the whole atmosphere supports the reasonableness of our estimation of excess attenuation.

  5. Evaluation of attenuation corrections using Monte Carlo simulated lung SPECT

    NASA Astrophysics Data System (ADS)

    Gustafsson, Agnetha; Bake, Björn; Jacobsson, Lars; Johansson, Åke; Ljungberg, Michael; Moonen, Michaela

    1998-08-01

    SPECT (single photon emission computed tomography) images are distorted by photon attenuation. The effect is complex in the thoracic region due to different tissue densities. This study compares the effect on the image homogeneity of two different methods of attenuation correction in lung SPECT; one pre-processing and one post-processing method. This study also investigates the impact of attenuation correction parameters such as lung contour, body contour, density of the lung tissue and effective attenuation coefficient. The Monte Carlo technique was used to simulate SPECT studies of a digital thorax phantom containing a homogeneous activity distribution in the lung. Homogeneity in reconstructed images was calculated as the coefficient of variation (CV). The isolated effect of the attenuation correction was assessed by normalizing pixel values from the attenuation corrected lung by pixel values from the lung with no attenuation effects. Results show that the CV decreased from 12.8% with no attenuation correction to 4.4% using the post-processing method and true densities in the thoracic region. The impact of variations in the definition of the body contour was found to be marginal while the corresponding effect of variations in the lung contour was substantial.

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

    SciTech Connect

    Yamshchikov, Vladimir Manuvakhova, Marina; Rodriguez, Efrain

    2016-01-15

    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 E{sub 138}K and K{sub 279}M 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. - Highlights: • Further attenuation of a WN vaccine precursor is outlined. • Effect of SA14-14-2 attenuating mutations is tested. • Mechanism of attenuation is proposed and illustrated. • The need for additional attenuating mutations is justified.

  7. A live-attenuated Zika virus vaccine candidate induces sterilizing immunity in mouse models.

    PubMed

    Shan, Chao; Muruato, Antonio E; Nunes, Bruno T D; Luo, Huanle; Xie, Xuping; Medeiros, Daniele B A; Wakamiya, Maki; Tesh, Robert B; Barrett, Alan D; Wang, Tian; Weaver, Scott C; Vasconcelos, Pedro F C; Rossi, Shannan L; Shi, Pei-Yong

    2017-06-01

    Zika virus (ZIKV) infection of pregnant women can cause a wide range of congenital abnormalities, including microcephaly, in the infant, a condition now collectively known as congenital ZIKV syndrome. A vaccine to prevent or significantly attenuate viremia in pregnant women who are residents of or travelers to epidemic or endemic regions is needed to avert congenital ZIKV syndrome, and might also help to suppress epidemic transmission. Here we report on a live-attenuated vaccine candidate that contains a 10-nucleotide deletion in the 3' untranslated region of the ZIKV genome (10-del ZIKV). The 10-del ZIKV is highly attenuated, immunogenic, and protective in type 1 interferon receptor-deficient A129 mice. Crucially, a single dose of 10-del ZIKV induced sterilizing immunity with a saturated neutralizing antibody titer, which no longer increased after challenge with an epidemic ZIKV, and completely prevented viremia. The immunized mice also developed a robust T cell response. Intracranial inoculation of 1-d-old immunocompetent CD-1 mice with 1 × 10(4) infectious focus units (IFU) of 10-del ZIKV caused no mortality, whereas infections with 10 IFU of wild-type ZIKV were lethal. Mechanistically, the attenuated virulence of 10-del ZIKV may be due to decreased viral RNA synthesis and increased sensitivity to type-1-interferon inhibition. The attenuated 10-del ZIKV was incapable of infecting mosquitoes after oral feeding of spiked-blood meals, representing an additional safety feature. Collectively, the safety and efficacy results suggest that further development of this promising, live-attenuated ZIKV vaccine candidate is warranted.

  8. Attenuation of Cavity Bay Noise

    DTIC Science & Technology

    2012-10-01

    amplification, known as peaking. Overall, the palliative devices based on resonant arrays have demonstrated high levels of attenuation which are...when the resonant frequency condition is met. The attenuation from a Helmholtz type resonator is achieved through frictional losses, vortex shedding...3 the λ/4 condition can be fulfilled and therefore porous mesh devices may not be able to provide a high level of attenuation . Resonant arrays

  9. 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.

  10. 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.

  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. 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.

  13. 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

  14. 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.

  15. 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.

  16. NATURAL ATTENUATION OF CHLORINATED SOLVENTS IN GROUND WATER

    EPA Science Inventory

    There are a variety of mechanisms that destroy chlorinated solvents in ground water, including reductive dechlorination (biotic or abiotic), dehydrochloroelimination (abiotic), and hydrolysis (biotic or abiotic). Most proposals for Monitored Natural Attenuation (MNA) of chlorina...

  17. 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.

  18. Signature of seismic wave attenuation during fracture network formation

    NASA Astrophysics Data System (ADS)

    Barnhoorn, Auke; Zhubayev, Alimzhan; Houben, Maartje; Hardebol, Nico; Smeulders, David

    2015-04-01

    Seismic waves are significantly affected by the presence of fractures and faults. Fractures alter the arrival time of a seismic wave and the amplitude of the seismic wave. Attenuation of a seismic wave is the reduction of wave amplitude due to the presence of e.g. fractures. Attenuation of acoustic compressional P- and shear S-waves have been measured in laboratory studies on different rock types. These studies generally show a decrease in attenuation with an increase in stress. This decrease in attenuation is attributed to progressive crack closure of pre-existing cracks. The stress-dependent decrease in attenuation reported in these studies all occur within the elastic deformation field, i.e. below yield stress levels and thus no additional cracks/micro-fractures have yet been formed. At stress levels just above the yield strength the first fractures start to form. With increasing stress, fractures nucleate, grow and coalesce until a connected network of fractures has developed at which failure of the rock sample occurs. The change in attenuation during the fracturing process however has seldom been investigated. In analogy to fracture closure, where attenuation generally decreases, fracture formation should cause again an increase in attenuation. Here we report an experimental study on shales from Whitby (UK), where s-wave attenuation was measured in the laboratory during an increase in stress towards fracture formation until complete failure of the shale samples. Before yield stress conditions, as expected an increase in stress caused a gradual decrease in attenuation. At the transition from elastic to inelastic deformation behaviour, the first microfractures start to form and attenuation starts to increase again. This reversal in attenuation behaviour could potentially be used as an indicator that failure of a rock mass under stress is imminent (imminence of seismicity). The measured seismic velocities do not depict the transition from elastic to inelastic

  19. 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…

  20. 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…

  1. Training on hearing protector insertion improves noise attenuation.

    PubMed

    Samelli, Alessandra Giannella; Rocha, Clayton Henrique; Theodósio, Patrícia; Moreira, Renata Rodrigues; Neves-Lobo, Ivone Ferreira

    2015-01-01

    To determine the efficacy of hearing protector insertion by comparing attenuation values measured by objective (MIRE) and subjective (REAT) methods in groups with and without training. The study included 80 male subjects assigned to experimental (with training) and control (without training) groups. The following procedures were performed: occupational history, objective and subjective assessment of hearing protectors. Only subjects in the experimental group received training and guidance on proper hearing protector insertion. Attenuation values were significantly higher in the experimental group than in the control group at all frequencies (500, 1000, 2000, and 4000 Hz) investigated through the objective (MIRE) and subjective (REAT) methods. In addition, attenuation values in the control group were lower than those provided by the hearing protector manufacturer. Both objective and subjective attenuation tests demonstrated the efficacy of training on insertion of hearing protectors because the group that received training on proper hearing protection insertion exhibited higher attenuation values than the untrained group.

  2. Evolutionary History and Attenuation of Myxoma Virus on Two Continents

    PubMed Central

    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

  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.

  4. Detecting the EBL attenuation of blazars with GLAST

    NASA Astrophysics Data System (ADS)

    Reyes, Luis C.

    The Large Area Telescope (LAT) on board GLAST (Gamma-ray Large Area Space Telescope) due for launch in late 2007 will study the gamma-ray sky in the energy range 20 MeV to >300 GeV. GLAST-LAT's improved sensitivity with respect to previous missions will increase the number of known gamma-ray blazars from about 100 to thousands, with redshifts up to z~3-5. Since g-rays with energy above 10 GeV interact via pair-production with photons from the Extragalactic Background Light (EBL), the systematic attenuation of GLAST-detected blazars as a function of redshift would constitute and effective and unique probe of the optical-UV EBL density and its evolution over cosmic history. Analysis techniques introduced in this dissertation make use of the large number of blazars detected by GLAST to study the collective behavior of their spectra as a function of redshift. These techniques are shown to offer powerful ways to help separate the common level of attenuation due to the EBL from the intrinsic peculiarities of individual blazars. The capability of GLAST to perform these measurements depends in great measure on the acceptance of the instrument to high energy g-rays ( E > 10 GeV), which in previous space-experiments has been drastically reduced due to backsplash self-veto. This dissertation includes a study of the backsplash effect as measured with flight-like detectors during a beam test of the LAT calibration unit. This analysis was used to verify the capabilities of the GLAST simulations tools to reproduce backsplash effects.

  5. Lateral variations of seismic intensity attenuation in Italy

    NASA Astrophysics Data System (ADS)

    Carletti, Francescantonia; Gasperini, Paolo

    2003-12-01

    A tomographic study of the attenuation of seismic intensity in the Italian territory has been carried on the basis of a felt report database including more than 50 000 macroseismic observations. The spatial variations of the attenuation coefficients have been computed on meshes of 50 and 25 km and compared with other geophysical observables. By checkerboard and restore tests using a Gaussian error with a realistic amplitude of one intensity degree we verified that a selected set including about 20000 observations is able to reliably reproduce the imposed patterns. For the laterally varying attenuation model we also found a general reduction and a more uniform distribution of the average locality residual with respect to an isotropic attenuation law. The comparison of the inversion results with seismic velocity tomography of the crust and upper mantle shows fair correspondences between high-attenuation and low-velocity areas (Tyrrhenian slope of northern and central Apennines) as well as between low-attenuation and high-velocity ones (Po valley and Adriatic coast). The normalized attenuation functions computed for some areas of Italy also agree fairly well with empirical non-parametric attenuation functions determined by others, from accelerometer data. A clear correlation was found between the inferred behaviour of the slope of the attenuation function in the vicinity of the source (distance <45 km) and the heat flow. In fact, the most attenuating zones almost coincide with the highs of heat flow located along the northern Tyrrhenian coast of Tuscany and Latium and in the other volcanic areas (Campi Flegrei, Mount Etna, Colli Euganei and Monti Lessini). This clear correlation represents a convincing confirmation of the physical grounds on which the use and interpretation of macroseismic data is based.

  6. Role of natural attenuation in modeling the leaching of contaminants in the risk analysis framework.

    PubMed

    Verginelli, Iason; Baciocchi, Renato

    2013-01-15

    Natural attenuation (NA) processes occurring in the subsurface can significantly affect the impact on groundwater from contamination sources located in the vadose zone, especially when mobile and readily biodegradable compounds, such as BTEX, are present. Besides, in the last decades several studies have shown natural attenuation to take place also for more persistent compounds, such as Polycyclic Aromatic Hydrocarbons (PAHs). Nevertheless, common risk analysis frameworks, based on the ASTM RBCA (Risk Based Corrective Action) approach, do not include NA pathways in the fate and transport models, thus possibly leading to an overestimation of the calculated risk. The aim of this study was to provide an insight on the relevance of the different key natural attenuation processes usually taking place in the subsurface and to highlight for which contamination scenarios their inclusion in the risk-analysis framework could provide a more realistic risk assessment. To this end, an analytical model accounting for source depletion and biodegradation, dispersion and diffusion during leaching was developed and applied to several contamination scenarios. These scenarios included contamination by BTEX, characterized by relatively high mobility and biodegradation rate, and PAHs, i.e. a more persistent class of compounds. The obtained results showed that BTEX are likely to be attenuated in the source zone due to their mobility and ready biodegradation (assuming biodegradation constant rates in the order of 0.01-1 d(-1)). Instead, attenuation along transport through the vadose zone was found to be less important, as the residence time of the contaminant in the unsaturated zone is often too low with respect to the time required to get a relevant biodegradation of BTEX. On the other hand, heavier compounds such as PAHs, were found to be attenuated during leaching since the residence time in the vadose zone can reach values up to thousands of years. In these cases, even with the

  7. Shear wave velocity and attenuation in the upper layer of ocean bottoms from long-range acoustic field measurements.

    PubMed

    Zhou, Ji-Xun; Zhang, Xue-Zhen

    2012-12-01

    Several physics-based seabed geoacoustic models (including the Biot theory) predict that compressional wave attenuation α(2) in sandy marine sediments approximately follows quadratic frequency dependence at low frequencies, i.e., α(2)≈kf(n) (dB/m), n=2. A recent paper on broadband geoacoustic inversions from low frequency (LF) field measurements, made at 20 locations around the world, has indicated that the frequency exponent of the effective sound attenuation n≈1.80 in a frequency band of 50-1000 Hz [Zhou et al., J. Acoust. Soc. Am. 125, 2847-2866 (2009)]. Carey and Pierce hypothesize that the discrepancy is due to the inversion models' neglect of shear wave effects [J. Acoust. Soc. Am. 124, EL271-EL277 (2008)]. The broadband geoacoustic inversions assume that the seabottom is an equivalent fluid and sound waves interact with the bottom at small grazing angles. The shear wave velocity and attenuation in the upper layer of ocean bottoms are estimated from the LF field-inverted effective bottom attenuations using a near-grazing bottom reflection expression for the equivalent fluid model, derived by Zhang and Tindle [J. Acoust. Soc. Am. 98, 3391-3396 (1995)]. The resultant shear wave velocity and attenuation are consistent with the SAX99 measurement at 25 Hz and 1000 Hz. The results are helpful for the analysis of shear wave effects on long-range sound propagation in shallow water.

  8. 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.

  9. LCLS XTOD Attenuator System System Concept Report

    SciTech Connect

    Kishiyama, K; Roeben, M; Trent, J; Ryutov, D; Shen, S

    2006-04-12

    The attenuator system for the Linac Coherent Light Source (LCLS) X-ray Transport, Optics and Diagnostics (XTOD) system has been configured and analyzed by the Lawrence Livermore National Laboratory's New Technologies Engineering Division (NTED) as requested by the SLAC/LCLS program. The system layout, performance analyses and selection of the vacuum components are presented in this System Conceptual Review (SCR) report. Also included are the plans for prototype, procurement, mechanical integration, and the cost estimates.

  10. A Citizen's Guide to Monitored Natural Attenuation

    EPA Pesticide Factsheets

    Citizen's Guide describing how natural attenuation relies on natural processes to decrease or attenuate concentrations of contaminants in soil and groundwater. Scientists monitor these conditions to make sure natural attenuation is working.

  11. Bioventing and natural attenuation: The combination of in situ treatment technologies provide effective site remediation

    SciTech Connect

    Brown, K.; Malloy, J.; Sekerka, P.; Sibbett, B.; Thomas, M.; Tyner, L.; Zhong, J.; Caron, D.

    1995-12-31

    IT Corporation (IT) is evaluating the combination of free product removal, bioventing, and natural attenuation for remediation of jet fuel-impacted soil and groundwater at George Air Force Base, California. Remedial activities are focused on a 155-acre benzene and 27-acre free product plume which have resulted from a leaking liquid fuels distribution system. In situ remedial options are favored at this site due to the reduced yield of the aquifer, low groundwater velocity, large areal extent of contamination, reduced risk of exposure, and ongoing site operations. Following the completion of a long-term monitoring investigation including bioventing pilot operations, natural attenuation monitoring, and free product recovery, remedial designs will be formalized.

  12. 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.

  13. 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.

  14. Practitioner perceptions of attenuated psychosis syndrome.

    PubMed

    Jacobs, Elizabeth; Kline, Emily; Schiffman, Jason

    2011-09-01

    The "Attenuated Psychosis Syndrome" (APS, sometimes referred to as the "schizophrenia prodrome") is characterized by subthreshold psychotic-like symptoms and functional decline, and is often associated with significant disability. These symptoms may cause impairment and are of further interest due to their predictive relation to schizophrenia and other psychotic disorders. These symptoms currently are not represented in the diagnostic system for mental health, and it is unclear how they are conceptualized by relevant professionals. The current study surveyed a national sample (n=303) of clinical psychologists, psychiatrists, and general practitioners regarding their clinical appraisal of APS. Practitioners were asked to respond to vignettes representing three conditions: psychosis, subthreshold psychosis (indicating 'attenuated' psychosis symptoms), and no psychotic symptoms. Practitioners' responses suggested that APS is viewed consistently with a DSM-IV-TR defined mental disorder and that most clinicians may diagnose this condition as a full threshold psychotic disorder. Findings tentatively suggest that the inclusion of an attenuated psychosis symptoms category in the forthcoming DSM-5 may be helpful in improving diagnostic reliability and facilitating best practice among community practitioners.

  15. 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.

  16. Theoretical Analysis of Rain Attenuation Probability

    NASA Astrophysics Data System (ADS)

    Roy, Surendra Kr.; Jha, Santosh Kr.; Jha, Lallan

    2007-07-01

    Satellite communication technologies are now highly developed and high quality, distance-independent services have expanded over a very wide area. As for the system design of the Hokkaido integrated telecommunications(HIT) network, it must first overcome outages of satellite links due to rain attenuation in ka frequency bands. In this paper theoretical analysis of rain attenuation probability on a slant path has been made. The formula proposed is based Weibull distribution and incorporates recent ITU-R recommendations concerning the necessary rain rates and rain heights inputs. The error behaviour of the model was tested with the loading rain attenuation prediction model recommended by ITU-R for large number of experiments at different probability levels. The novel slant path rain attenuastion prediction model compared to the ITU-R one exhibits a similar behaviour at low time percentages and a better root-mean-square error performance for probability levels above 0.02%. The set of presented models exhibits the advantage of implementation with little complexity and is considered useful for educational and back of the envelope computations.

  17. The Gas Attenuator of FLASH at DESY

    SciTech Connect

    Hahn, Ulrich; Tiedtke, Kai

    2007-01-19

    FLASH (Free electron LASer at Hamburg) as a part of the Deutsches Elektronen Synchroton DESY is the first Free Electron Laser (FEL) user facility for VUV and soft X-ray coherent light experiments. The SASE (Self Amplification by Stimulated Emission) process generates ultra short coherent radiation pulses on the femtosecond time scale with peak powers in the GW range. Several experiments need reliable means to reduce the FEL intensity over many orders of magnitude without changing the photon beam characteristics. Since a reduction of the FEL intensity by variation of machine parameters is not appropriate, a windowless gas-filled cell in combination with differential pumping units is used for attenuating the FEL radiation. This attenuator is placed in the beamline in outside the experimental hall. The total length of the gas cell is 15 m and the maximum gas pressure, which can be handled by the differential pumping units, is about 0.1 mbar. The attenuation range of Nitrogen covers at least 5 orders of magnitude in the spectral range of 19 to 120 nm due to its large absorption cross section. Between 19 and 9 nm and for shorter wavelengths Xenon and Krypton can be used, respectively.

  18. Thin-Layering Effect On Estimating Seismic Attenuation In Methane Hydrate-Bearing Sediments

    NASA Astrophysics Data System (ADS)

    Lee, K.; Matsushima, J.

    2012-12-01

    Seismic attenuation is one of the important parameters that provide information concerning both the detection and quantitative assessment of gas-hydrates. We estimated seismic attenuation (1/Q) from surface seismic data acquired at Nankai Trough in Japan. We adapt the Q-versus offset (QVO) method to calculate robust and continuous interval attenuations from CMP gathers. We could observe high attenuation in methane hydrate bearing sediments over the BSR region. However some negative 1/Q values are also shown. This means that the amplitude of high frequency components is increasing with depth. Such results may be due to tuning effect. Here, we carried out numerical test to see how thin-layering effect influences on seismic attenuation results. The results showed that tuning considerably influences the attenuation results, and causes the lower 1/Q values (lower attenuation) and negative 1/Q values.

  19. Including Jews in Multiculturalism.

    ERIC Educational Resources Information Center

    Langman, Peter F.

    1995-01-01

    Discusses reasons for the lack of attention to Jews as an ethnic minority within multiculturalism both by Jews and non-Jews; why Jews and Jewish issues need to be included; and addresses some of the issues involved in the ethical treatment of Jewish clients. (Author)

  20. Absolute measurement of optical attenuation

    NASA Astrophysics Data System (ADS)

    Wetsel, Grover C., Jr.; Stotts, Steven A.

    1983-06-01

    We have discovered that laser beam deflection spectroscopy can be used for the absolute measurement of wave or particle beam attenuation in condensed matter. The concept has been experimentally evaluated by successfully measuring the absolute optical attenuation in a crystal of U3+:CaF2 at 514 nm. A theoretical model that explains the experiment and characterizes the range of applicability of the method has been developed.

  1. Physiological and Perceptual Sensory Attenuation Have Different Underlying Neurophysiological Correlates

    PubMed Central

    Davare, Marco; Kilner, James M.

    2016-01-01

    Sensory attenuation, the top-down filtering or gating of afferent information, has been extensively studied in two fields: physiological and perceptual. Physiological sensory attenuation is represented as a decrease in the amplitude of the primary and secondary components of the somatosensory evoked potential (SEP) before and during movement. Perceptual sensory attenuation, described using the analogy of a persons' inability to tickle oneself, is a reduction in the perception of the afferent input of a self-produced tactile sensation due to the central cancellation of the reafferent signal by the efference copy of the motor command to produce the action. The fields investigating these two areas have remained isolated, so the relationship between them is unclear. The current study delivered median nerve stimulation to produce SEPs during a force-matching paradigm (used to quantify perceptual sensory attenuation) in healthy human subjects to determine whether SEP gating correlated with the behavior. Our results revealed that these two forms of attenuation have dissociable neurophysiological correlates and are likely functionally distinct, which has important implications for understanding neurological disorders in which one form of sensory attenuation but not the other is impaired. Time–frequency analyses revealed a negative correlation over sensorimotor cortex between gamma-oscillatory activity and the magnitude of perceptual sensory attenuation. This finding is consistent with the hypothesis that gamma-band power is related to prediction error and that this might underlie perceptual sensory attenuation. SIGNIFICANCE STATEMENT We demonstrate that there are two functionally and mechanistically distinct forms of sensory gating. The literature regarding somatosensory evoked potential (SEP) gating is commonly cited as a potential mechanism underlying perceptual sensory attenuation; however, the formal relationship between physiological and perceptual sensory

  2. 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.

  3. Ultrasonic attenuation in parallel-nylon-wire cancellous-bone-mimicking phantoms.

    PubMed

    Wear, Keith A

    2008-12-01

    Attenuation coefficients between 1.5 and 3.5 MHz were measured on four parallel-nylon-wire arrays (simulating cancellous bone) with four different wire diameters (150, 200, 250, and 300 microm). Interwire spacing was 800 microm for all four parallel-nylon-wire arrays. The measured frequency dependencies of attenuation were consistent with theoretical predications based on Faran's theory, which considers the component of attenuation due to scattering of longitudinal waves.

  4. 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

  5. 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).

  6. Proteomic Analysis of Pathogenic and Attenuated Alcelaphine Herpesvirus 1▿

    PubMed Central

    Dry, Inga; Haig, David M.; Inglis, Neil F.; Imrie, Lisa; Stewart, James P.; Russell, George C.

    2008-01-01

    The gammaherpesvirus alcelaphine herpesvirus 1 (AlHV-1) causes malignant catarrhal fever in susceptible ungulates but infects its natural host, wildebeest, without obvious clinical signs. In tissue culture, AlHV-1 is initially predominantly cell associated and virulent but on extended culture becomes cell-free and attenuated. We wanted to determine what changes in protein composition had taken place during the transition from virulent to attenuated virus in culture. Purified virus preparations were fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and proteins were analyzed by liquid chromatography-electrospray ionization-tandem mass spectrometry. Peptides were identified in serial gel slices by using MASCOT software to interrogate virus-specific and nonredundant sequence databases. Twenty-three AlHV-1-encoded proteins and six cellular proteins were identified in the attenuated and virulent viruses. Two polypeptides were detected in only the virulent virus preparations, while one other protein was found in only the attenuated virus. Two of these virus-specific proteins were identified by a single peptide, suggesting that these may be low-abundance virion proteins rather than markers of attenuation or pathogenesis. The results suggest that attenuation of AlHV-1 is not the result of gross changes in the composition of the virus particle but probably due to altered viral gene expression in the infected cell. PMID:18353942

  7. Correction for acoustic attenuation effects in optoacoustic tomographic reconstructions

    NASA Astrophysics Data System (ADS)

    Deán-Ben, X. Luís; Razansky, Daniel; Ntziachristos, Vasilis

    2011-07-01

    The feasibility of correcting for the effects of acoustic attenuation in optoacoustic tomographic reconstructions obtained with model-based inversion is shown in this work. Acoustic attenuation is a physical phenomenon that takes place inevitably in actual acoustic media and becomes significant at high ultrasonic frequencies. The frequency dependence of acoustic attenuation and the associated dispersion lead to reduction of amplitude and broadening of the optoacoustic signals, which in turn cause, respectively, quantification errors and loss of resolution in the reconstructed images. In this work we imaged an agar phantom with embedded microparticles in three different scenarios, namely with the signals acquired with no attenuation, with the signals collected by placing an attenuating sample in between the phantom and the ultrasonic transducer and with the signals corrected for the effects of acoustic attenuation. The results obtained show that the quantification inaccuracies and the loss of resolution of the images can be partially corrected at the expense of introducing noise at high spatial frequencies due to the amplification of the high frequency components of the noise in the signals.

  8. Three-dimensional P- and S-wave attenuation structures around the source region of the 2016 Kumamoto earthquakes

    NASA Astrophysics Data System (ADS)

    Komatsu, Masanao; Takenaka, Hiroshi; Oda, Hitoshi

    2017-07-01

    We investigate the three-dimensional P- and S-wave attenuation (QP^{ - 1} and QS^{ - 1} ) structures of the crust around the source region of the 2016 Kumamoto earthquakes, Japan. To estimate the attenuation structures, the path-averaged attenuation factor t^{*} is estimated from the amplitude decay rate of the P- and S-wave spectra corrected for the source spectrum. The QP^{ - 1} and QS^{ - 1} structures are estimated by tomography using t^{*} for the P- and S-waves, respectively. Several features are found in the attenuation structures as follows: In the source region, two high-QP and high-QS zones exist along the Futagawa and the Hinagu fault segments in the upper crust. The high-QP and high-QS zone along the Futagawa fault segment is found to include the large-slip area of the mainshock obtained from a source inversion study. In the lower crust, the low QP is distributed beneath the entire source region. A low-QP and low-QS zone also exists beneath the Kuju and Aso volcanoes, which is consistent with the shallow limited depth extent of the seismogenic zone due to high temperature. The western edge of this zone adjoins the eastern edge of the high-QP and high-QS area, including the large-slip area.[Figure not available: see fulltext.

  9. Next Generation Attenuation Relationships for the Eastern United States (NGA-East)

    SciTech Connect

    Mahin, Stephen; Bozorgnia, Yousef

    2016-04-11

    This is a progress report to DOE for project Next Generation Attenuation for Central & Eastern US (NGA-East).This progress report consists of numerous monthly progress segments starting June 1, 2010 until December 31, 2015. Please note: the December 2015 progress report was issued in January 2016 due to the final university financial reporting at the end of this project. For each month, there is a technical progress list, and an update on the financial progress of the project. As you know, this project is jointly funded by the DOE, US Nuclear Regulatory Commission (NRC) and Electric Power Research Institute (EPRI). Thus, each segment includes financial progress for these three funding agencies.

  10. 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.

  11. Nutritional therapies (including fosteum).

    PubMed

    Nieves, Jeri W

    2009-03-01

    Nutrition is important in promoting bone health and in managing an individual with low bone mass or osteoporosis. In adult women and men, known losses of bone mass and microarchitecture occur, and nutrition can help minimize these losses. In every patient, a healthy diet with adequate protein, fruits, vegetables, calcium, and vitamin D is required to maintain bone health. Recent reports on nutritional remedies for osteoporosis have highlighted the importance of calcium in youth and continued importance in conjunction with vitamin D as the population ages. It is likely that a calcium intake of 1200 mg/d is ideal, and there are some concerns about excessive calcium intakes. However, vitamin D intake needs to be increased in most populations. The ability of soy products, particularly genistein aglycone, to provide skeletal benefit has been recently studied, including some data that support a new medical food marketed as Fosteum (Primus Pharmaceuticals, Scottsdale, AZ).

  12. Attenuation and Velocity tomography can we join them?

    NASA Astrophysics Data System (ADS)

    Debski, Wojciech

    2013-04-01

    Velocity tomography, is now routinely used to image velocity distributions which are subsequently interpreted in terms of the Earth or rock-sample structure. This technique has been successfully used in detailed mapping of the Earth in various scales ranging from the whole globe until very local rock-mass structure, e.g. in mines. It is also used in geo-technical (tunnels, mines, water dams, etc.) and laboratory measurements. The second tomography technique, namely attenuation tomography, is used to image another physical property of rocks: the acoustic attenuation structure usually describe by the parameter Q. This technique is, however, much more difficult than velocity tomography because the attenuation of seismic/acoustic waves is a much more subtle effect than a variation of delays of energy arrival times due to velocity heterogeneities. There exist a lot of factors that can easily disturb attenuation measurements so it is difficult to obtain a reliable image of the attenuation structure. For this reason, a very high quality of data used for attenuation tomography must be ensured. Nevertheless, the additional effort necessary to obtain an image of Q is worthwhile because Q is regarded to be more sensitive to the rock structure than seismic/acoustic wave velocity. Imaging the Q distribution can be achieved by inverting various characteristics of the measured signals: amplitudes, spectra decay, pulse broadening or central frequency shift. The advantages and limitations of each of these approaches are well known. In this presentation we discuss the approach developed for the acoustic ultrasonic tomography imaging and called Enhanced Velocity Tomography and possibility of its using in a ``global seismological'' framework. It consists in a combination of both velocity and attenuation tomography into one scheme to maximize the advantage of the robustness of velocity and the sensitivity to the micro-structure of attenuation.

  13. 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.

  14. Post-retrieval extinction attenuates cocaine memories.

    PubMed

    Sartor, Gregory C; Aston-Jones, Gary

    2014-04-01

    Recent studies have shown that post-retrieval extinction training attenuates fear and reward-related memories in both humans and rodents. This noninvasive, behavioral approach has the potential to be used in clinical settings to treat maladaptive memories that underlie several psychiatric disorders, including drug addiction. However, few studies to date have used a post-retrieval extinction approach to attenuate addiction-related memories. In the current study, we attempted to disrupt cocaine-related memories by using the post-retrieval extinction paradigm in male Sprague Dawley rats. Results revealed that starting extinction training 1 h after cocaine contextual memory was retrieved significantly attenuated cocaine-primed reinstatement of conditioned place preference (CPP) and relapse of cocaine CPP (drug-free and cocaine-primed) following 30 days of abstinence. However, animals that did not retrieve the contextual cocaine memory before extinction training, or animals that began extinction training 24 h after retrieval (outside of the reconsolidation window), demonstrated normal cocaine CPP. Conversely, animals that received additional CPP conditioning, rather than extinction training, 1 h after reactivation of cocaine memory showed enhanced cocaine CPP compared with animals that did not reactivate the cocaine memory before conditioning. These results reveal that a behavioral manipulation that takes advantage of reconsolidation and extinction of drug memories may be useful in decreasing preference for, and abuse of, cocaine.

  15. 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.

  16. 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.

  17. 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.

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

    PubMed Central

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

    2016-01-01

    Summary 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

  19. Refraction, including prisms.

    PubMed

    Hiatt, R L

    1991-02-01

    The literature in the past year on refraction is replete with several isolated but very important topics that have been of interest to strabismologists and refractionists for many decades. The refractive changes in scleral buckling procedures include an increase in axial length as well as an increase in myopia, as would be expected. Tinted lenses in dyslexia show little positive effect in the nonasthmatic patients in one study. The use of spectacles or bifocals as a way to control increase in myopia is refuted in another report. It has been shown that in accommodative esotropia not all patients will be able to escape the use of bifocals in the teenage years, even though surgery might be performed. The hope that disposable contact lenses would cut down on the instance of giant papillary conjunctivitis and keratitis has been given some credence, and the conventional theory that sclerosis alone is the cause of presbyopia is attacked. Also, gas permeable bifocal contact lenses are reviewed and the difficulties of correcting presbyopia by this method outlined. The practice of giving an aphakic less bifocal addition instead of a nonaphakic, based on the presumption of increased effective power, is challenged. In the review of prisms, the majority of articles concern prism adaption. The most significant report is that of the Prism Adaptation Study Research Group (Arch Ophthalmol 1990, 108:1248-1256), showing that acquired esotropia in particular has an increased incidence of stable and full corrections surgically in the prism adaptation group versus the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

  20. Attenuation of concentration fluctuations of water vapor and other trace gases in turbulent tube flow

    Treesearch

    W. J. Massman; A. Ibrom

    2008-01-01

    Recent studies with closed-path eddy covariance (EC) systems have indicated that the attenuation of fluctuations of water vapor concentration is dependent upon ambient relative humidity, presumably due to sorption/desorption of water molecules at the interior surface of the tube. Previous studies of EC-related tube attenuation effects have either not considered this...

  1. 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.

  2. 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.

  3. Attenuation of Landfill Leachate In Unsaturated Sandstone

    NASA Astrophysics Data System (ADS)

    Butler, A. P.; Brook, C.; Godley, A.; Lewin, K.; Young, C. P.

    Landfill leachate emanating from old "dilute and disperse" sites represents a potential (and in many cases actual) threat to the integrity of groundwater. Indeed, this concern has been included in EU legislation (80/86/EEC), where key contaminants (e.g. ammonia, various toxic organic compounds and heavy metals) are explicitly highlighted in terms of their impact on groundwater. In the UK, whilst there are a substantial number of unlined landfills sited on major aquifers, many of these are in locations where there is a substantial unsaturated zone. Thus, there exists the opportunity for the modification and attenuation of contaminants prior to it encountering the water table. An understanding of likely changes in leachate content and concentrations at such sites will enable a more comprehensive assessment of the potential risks and liabilities posed by such sites to be evaluated. The Burntstump landfill, situated 8 km north of Nottingham (UK), is sited on an outcrop of Sherwood sandstone. The fine friable sand has been quarried since the 1960s and the excavated volume used to store municipal waste. Filling at the site commenced in the mid 1970s and originally was unlined. In 1978 the first of what was to become a series of boreholes was installed within an area of roughly 5 m radius over one of the original waste cells. Cores of the waste and underlying sandstone were extracted and analysed for a range of physical and chemical parameters. The most recent set of analyses were obtained in 2000. The series of investigations therefore provide an important record of leachate migration and modification through the unsaturated zone for over twenty years. The progression of the leachate front is clearly delineated by the chloride concentration profile with an average velocity of around 1.6 m.yr-1. Combining this value with an average (and reasonably uniform) measured moisture content of about 7% gives a mean inter-granular specific discharge of 110 mm.yr-1. An interesting

  4. Credit where due.

    PubMed

    Friedman, Steven G

    2016-08-01

    The history of medicine is filled with stories of tireless researchers who failed to get credit for their hard work. Examples of this include Rosalind Franklin, who helped to elucidate the structure of DNA; Frederick Banting, who helped to discover insulin; and Jay McLean, who discovered heparin. The founding of the field of vascular surgery provides one of the most vivid examples of uncredited work. Even though Alexis Carrel was an unpaid, untitled assistant in Charles Guthrie's laboratory, it was Carrel alone who received a Nobel Prize for their work. In an attempt to give credit where due, the reasons for this injustice are described. Copyright © 2016 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.

  5. 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.

  6. 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.

  7. 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.

  8. 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).

  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. High seismic attenuation at a mid-ocean ridge reveals the distribution of deep melt

    PubMed Central

    Eilon, Zachary C.; Abers, Geoffrey A.

    2017-01-01

    At most mid-ocean ridges, a wide region of decompression melting must be reconciled with a narrow neovolcanic zone and the establishment of full oceanic crustal thickness close to the rift axis. Two competing paradigms have been proposed to explain melt focusing: narrow mantle upwelling due to dynamic effects related to in situ melt or wide mantle upwelling with lateral melt transport in inclined channels. Measurements of seismic attenuation provide a tool for identifying and characterizing the presence of melt and thermal heterogeneity in the upper mantle. We use a unique data set of teleseismic body waves recorded on the Cascadia Initiative’s Amphibious Array to simultaneously measure seismic attenuation and velocity across an entire oceanic microplate. We observe maximal differential attenuation and the largest delays (ΔtS*~1.7 s and δTS ~ 2 s) in a narrow zone <50 km from the Juan de Fuca and Gorda ridge axes, with values that are not consistent with laboratory estimates of temperature or water effects. The implied seismic quality factor (Qs ≤ 25) is among the lowest observed worldwide. Models harnessing experimentally derived anelastic scaling relationships require a 150-km-deep subridge region containing up to 2% in situ melt. The low viscosity and low density associated with this deep, narrow melt column provide the conditions for dynamic mantle upwelling, explaining a suite of geophysical observations at ridges, including electrical conductivity and shear velocity anomalies. PMID:28560338

  11. Investigation of the influence of reflection on the attenuation of cancellous bone.

    PubMed

    Klinge, Sandra; Hackl, Klaus; Gilbert, Robert P

    2013-01-01

    The model proposed in this paper is based on the fact that the reflection might have a significant contribution to the attenuation of the acoustic waves propagating through the cancellous bone. The numerical implementation of the mentioned effect is realized by the development of a new representative volume element that includes an infinitesimally thin 'transient' layer on the contact surface of the bone and the marrow. This layer serves to model the amplitude transformation of the incident wave by the transition through media with different acoustic impedances and to take into account the energy loss due to the reflection. The proposed representative volume element together with the multiscale finite element is used to simulate the wave propagation and to evaluate the attenuation coefficient for samples with different effective densities in the dependence of the applied excitation frequency. The obtained numerical values show a very good agreement with the experimental results. Moreover, the model enables the determination of the upper and the lower bound for the attenuation coefficient.

  12. 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.

  13. High seismic attenuation at a mid-ocean ridge reveals the distribution of deep melt.

    PubMed

    Eilon, Zachary C; Abers, Geoffrey A

    2017-05-01

    At most mid-ocean ridges, a wide region of decompression melting must be reconciled with a narrow neovolcanic zone and the establishment of full oceanic crustal thickness close to the rift axis. Two competing paradigms have been proposed to explain melt focusing: narrow mantle upwelling due to dynamic effects related to in situ melt or wide mantle upwelling with lateral melt transport in inclined channels. Measurements of seismic attenuation provide a tool for identifying and characterizing the presence of melt and thermal heterogeneity in the upper mantle. We use a unique data set of teleseismic body waves recorded on the Cascadia Initiative's Amphibious Array to simultaneously measure seismic attenuation and velocity across an entire oceanic microplate. We observe maximal differential attenuation and the largest delays ([Formula: see text] s and δTS ~ 2 s) in a narrow zone <50 km from the Juan de Fuca and Gorda ridge axes, with values that are not consistent with laboratory estimates of temperature or water effects. The implied seismic quality factor (Qs ≤ 25) is among the lowest observed worldwide. Models harnessing experimentally derived anelastic scaling relationships require a 150-km-deep subridge region containing up to 2% in situ melt. The low viscosity and low density associated with this deep, narrow melt column provide the conditions for dynamic mantle upwelling, explaining a suite of geophysical observations at ridges, including electrical conductivity and shear velocity anomalies.

  14. 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.

  15. 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.

  16. 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.

  17. Cangrelor attenuates coated-platelet formation.

    PubMed

    Norgard, Nicholas B; Hann, Callie L; Dale, George L

    2009-01-01

    P2Y(12) inhibitors were introduced clinically as effective inhibitors of adenosine-5'-diphosphate (ADP) mediated platelet activation and aggregation. This class of pharmacological agents has enjoyed considerable success. Cangrelor is a recently developed P2Y(12) inhibitor that has the advantage of being an active drug not requiring metabolic conversion, although it is not orally available. Coated-platelets are a subclass of activated platelets generated on dual agonist activation with collagen plus thrombin; the primary hallmark of coated-platelets is their ability to support prothrombinase activity. Interestingly, we recently observed that the relatively weak agonist ADP potentiates the production of coated-platelets by the very strong agonists collagen plus thrombin, a previously unknown role for ADP. The authors sought in this study to determine if P2Y(12) inhibitors, such as cangrelor, were capable of attenuating this augmentation of coated-platelet generation. Cangrelor, at physiologically relevant concentrations, was able to eliminate the ADP-dependent increase in coated-platelet production with an IC(50) of 1.4 nM. Cangrelor, however, had no effect on thrombin-dependent platelet activation as measured by P-selectin expression. Although this in vitro study does not address the question of whether the effectiveness of cangrelor in vivo is partially due to an attenuation of coated-platelet production in addition to its documented antiaggregatory effects, it does reveal an unexpected action of cangrelor. Additional studies will be required to determine if all P2Y(12) inhibitors are equally effective in attenuating coated-platelet production.

  18. 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.

  19. 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.

  20. Attenuation of Scalar Fluxes Measured with Spatially-displaced Sensors

    NASA Astrophysics Data System (ADS)

    Horst, T. W.; Lenschow, D. H.

    2009-02-01

    Observations from the Horizontal Array Turbulence Study (HATS) field program are used to examine the attenuation of measured scalar fluxes caused by spatial separation between the vertical velocity and scalar sensors. The HATS data show that flux attenuation for streamwise, crosswind, and vertical sensor displacements are each a function of a dimensionless, stability-dependent parameter n m multiplied by the ratio of sensor displacement to measurement height. The scalar flux decays more rapidly with crosswind displacements than for streamwise displacements and decays more rapidly for stable stratification than for unstable stratification. The cospectral flux attenuation model of Kristensen et al. agrees well with the HATS data for streamwise sensor displacements, although it is necessary to include a neglected quadrature spectrum term to explain the observation that flux attenuation is often less with the scalar sensor downwind of the anemometer than for the opposite configuration. A simpler exponential decay model provides good estimates for crosswind sensor displacements, as well as for streamwise sensor displacements with stable stratification. A model similar to that of Lee and Black correctly predicts flux attenuation for a combination of streamwise and crosswind displacements, i.e. as a function of wind direction relative to the sensor displacement. The HATS data for vertical sensor displacements extend the near-neutral results of Kristensen et al. to diabatic stratification and confirm their finding that flux attenuation is less with the scalar sensor located below the anemometer than if the scalar sensor is displaced an equal distance either horizontally or above the anemometer.

  1. 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.

  2. Mechanisms for attenuation in cancellous-bone-mimicking phantoms.

    PubMed

    Wear, Keith A

    2008-11-01

    Broadband ultrasound attenuation (BUA) in cancellous bone is useful for prediction of osteoporotic fracture risk, but its causes are not well understood. To investigate attenuation mechanisms, 9 cancellous-bone-mimicking phantoms containing nylon filaments (simulating bone trabeculae) embedded within soft-tissue-mimicking fluid (simulating marrow) were interrogated. The measurements of frequency-dependent attenuation coefficient had 3 separable components: 1) a linear (with frequency) component attributable to absorption in the soft-tissue-mimicking fluid, 2) a quasilinear (with frequency) component, which may include absorption in and longitudinal-shear mode conversion by the nylon filaments, and 3) a nonlinear (with frequency) component, which may be attributable to longitudinal-longitudinal scattering by the nylon filaments. The slope of total linear (with frequency) attenuation coefficient (sum of components #1 and #2) versus frequency was found to increase linearly with volume fraction, consistent with reported measurements on cancellous bone. Backscatter coefficient measurements in the 9 phantoms supported the claim that the nonlinear (with frequency) component of attenuation coefficient (component #3) was closely associated with longitudinal-longitudinal scattering. This work represents the first experimental separation of these 3 components of attenuation in cancellous bone-mimicking phantoms.

  3. Impact of Scattering Model on Disdrometer Derived Attenuation Scaling

    NASA Technical Reports Server (NTRS)

    Zemba, Michael; Luini, Lorenzo; Nessel, James; Riva, Carlo (Compiler)

    2016-01-01

    NASA Glenn Research Center (GRC), the Air Force Research Laboratory (AFRL), and the Politecnico di Milano (POLIMI) are currently entering the third year of a joint propagation study in Milan, Italy utilizing the 20 and 40 GHz beacons of the Alphasat TDP5 Aldo Paraboni scientific payload. The Ka- and Q-band beacon receivers were installed at the POLIMI campus in June of 2014 and provide direct measurements of signal attenuation at each frequency. Collocated weather instrumentation provides concurrent measurement of atmospheric conditions at the receiver; included among these weather instruments is a Thies Clima Laser Precipitation Monitor (optical disdrometer) which records droplet size distributions (DSD) and droplet velocity distributions (DVD) during precipitation events. This information can be used to derive the specific attenuation at frequencies of interest and thereby scale measured attenuation data from one frequency to another. Given the ability to both predict the 40 GHz attenuation from the disdrometer and the 20 GHz timeseries as well as to directly measure the 40 GHz attenuation with the beacon receiver, the Milan terminal is uniquely able to assess these scaling techniques and refine the methods used to infer attenuation from disdrometer data.In order to derive specific attenuation from the DSD, the forward scattering coefficient must be computed. In previous work, this has been done using the Mie scattering model, however, this assumes a spherical droplet shape. The primary goal of this analysis is to assess the impact of the scattering model and droplet shape on disdrometer derived attenuation predictions by comparing the use of the Mie scattering model to the use of the T-matrix method, which does not assume a spherical droplet. In particular, this paper will investigate the impact of these two scattering approaches on the error of the resulting predictions as well as on the relationship between prediction error and rain rate.

  4. Impact of Scattering Model on Disdrometer Derived Attenuation Scaling

    NASA Technical Reports Server (NTRS)

    Zemba, Michael; Luini, Lorenzo; Nessel, James; Riva, Carlo

    2016-01-01

    NASA Glenn Research Center (GRC), the Air Force Research Laboratory (AFRL), and the Politecnico di Milano (POLIMI) are currently entering the third year of a joint propagation study in Milan, Italy utilizing the 20 and 40 GHz beacons of the Alphasat TDP#5 Aldo Paraboni scientific payload. The Ka- and Q-band beacon receivers were installed at the POLIMI campus in June of 2014 and provide direct measurements of signal attenuation at each frequency. Collocated weather instrumentation provides concurrent measurement of atmospheric conditions at the receiver; included among these weather instruments is a Thies Clima Laser Precipitation Monitor (optical disdrometer) which records droplet size distributions (DSD) and droplet velocity distributions (DVD) during precipitation events. This information can be used to derive the specific attenuation at frequencies of interest and thereby scale measured attenuation data from one frequency to another. Given the ability to both predict the 40 gigahertz attenuation from the disdrometer and the 20 gigahertz time-series as well as to directly measure the 40 gigahertz attenuation with the beacon receiver, the Milan terminal is uniquely able to assess these scaling techniques and refine the methods used to infer attenuation from disdrometer data. In order to derive specific attenuation from the DSD, the forward scattering coefficient must be computed. In previous work, this has been done using the Mie scattering model, however, this assumes a spherical droplet shape. The primary goal of this analysis is to assess the impact of the scattering model and droplet shape on disdrometer-derived attenuation predictions by comparing the use of the Mie scattering model to the use of the T-matrix method, which does not assume a spherical droplet. In particular, this paper will investigate the impact of these two scattering approaches on the error of the resulting predictions as well as on the relationship between prediction error and rain rate.

  5. 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.

  6. 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

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

    PubMed

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

    2014-02-01

    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. 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. 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 attenuator was relatively

  8. 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

  9. 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

  10. Attenuation of aqueous benzene in soils under saturated flow conditions.

    PubMed

    Kim, S-B; Kim, D-J; Yun, S-T

    2006-01-01

    The fate of aqueous benzene in subsurface was investigated in this study, focusing on the role of sorption and biodegradation on the benzene attenuation under dynamic flow conditions. Two sets of column tests were conducted in Plexiglass flow cells packed uniformly with sandy aquifer materials. The first set of the experiment was conducted with a step-type injection of benzene with different powder activated carbon (PAC) contents: (1) PAC = 0 %; (2) PAC = 0.5 %; (3) PAC = 2.0%. The second set was performed as a pulse-type with different test conditions: (4) benzene; (5) benzene and bacteria (Pseudomonas aeruginosa); (6) benzene and bacteria (P. aeruginosa) with hydrogen peroxide. In addition, numerical experiments were performed to examine the role of sorption processes on the benzene attenuation. In the step mode experiments, the KCl breakthrough curves (BTCs) reached the input concentration while the benzene BTCs were considerably lower than those of KCl with slight retardation for all cases, indicating that both reversible/retardation and irreversible sorption occurred. The pulse type tests showed that attenuation of benzene increased in the presence of bacteria due to biodegradation. The benzene attenuation by microbial degradation increased furthermore in the presence of hydrogen peroxide owing to sufficient supply of dissolved oxygen in soil column. Numerical experiments demonstrated that retardation could not contribute to the attenuation of benzene in soils but could only extend its breakthrough time. Experimental results indicated that aqueous benzene could be attenuated by irreversible sorption and biodegradation during transport through the subsurface. Additionally, the attenuation of aqueous benzene is closely related to organic carbon content and oxygen level existing in contaminated aquifers.

  11. 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.

  12. Broadband fractal acoustic metamaterials for low-frequency sound attenuation

    NASA Astrophysics Data System (ADS)

    Song, Gang Yong; Cheng, Qiang; Huang, Bei; Dong, Hui Yuan; Cui, Tie Jun

    2016-09-01

    We fabricate and experimentally characterize a broadband fractal acoustic metamaterial that can serve to attenuate the low-frequency sounds at selective frequencies ranging from 225 to 1175 Hz. The proposed metamaterials are constructed by the periodic Hilbert fractal elements made of photosensitive resin via 3D printing. In analogy to electromagnetic fractal structures, it is shown that multiple resonances can also be excited in the acoustic counterpart due to their self-similar properties, which help to attenuate the acoustic energy in a wide spectrum. The confinement of sound waves in such subwavelength element is evidenced by both numerical and experimental results. The proposed metamaterial may provide possible alternative for various applications such as the noise attenuation and the anechoic materials.

  13. Improvements in the spectral difference method for measuring ultrasonic attenuation.

    PubMed

    Insana, M; Zagzebski, J; Madsen, E

    1983-10-01

    The accuracy of the spectral difference method for measuring ultrasonic attenuation has been investigated using tissue-mimicking phantoms. Attenuation coefficients of the phantom materials were measured using a narrow-band substitution technique and compared with the results of the spectral difference method. Agreement within +/-10 percent was typical for measurements in homogeneous materials. The best agreement between the spectral difference and substitution techniques was obtained when effects due to transducer beam diffraction were taken into account in the analysis. This was found for two types of homogeneous tissue-mimicking materials, both having speed of sound and attenuation properties similar to human liver but each with different backscatter properties. The effects of inhomogeneous tissues interposed between the transducer and the interrogated volume were also studied by simulating these conditions in phantoms. Experimental techniques which minimize the effects of perturbations introduced by these inhomogeneities are suggested.

  14. Single Site Strong-Motion Attenuation Relationship

    NASA Astrophysics Data System (ADS)

    Sung, C.; Lee, C.

    2009-12-01

    The standard deviation of the logarithmic residuals in ground-motion prediction may directly influence the result of probabilistic seismic hazard analysis, especially in low probability. Therefore, “how to reduce the σ?” becomes an important issue in recent years. In most modern empirical ground motion studies, the total variability was separated into inter-event and intra-event components to distinction between epistemic uncertainty and aleatory uncertainty. Another approach is gaining control over the value of σ is to investigate in more detail the behavior of the individual components of variability with a single event or a single station (e.g., Niazi and Bozorgnia 1991; Ordaz and Reyes 1999; Jain et al. 2000; Atkinson 2006; Morikawa et al (2008)). In this study, we use the large data set available from the Taiwan Strong Motion Instrumentation Program (TSMIP) and select stations which recorded more than 700 strong-motion records (six stations). The ground motion attenuation is modified based on Campbell form which includes source term, distance term and site term Vs30. It is worth noting that a single site strong motion attenuation model does not include the site term, because the site is fixed at a station. Finally, we use hemisphere projection to show the path effect of residual in this study and compare the standard deviation for a single station (σi) and total stations (σT). We find that the single-station standard deviation is 20% smaller than the total standard deviation in this study and the result is better than Atkinson (2006). In the future work, a single source-region where occurred more than 5 earthquakes which triggered more than 50 stations will be selected for single source-region attenuation study.

  15. Perchlorate natural attenuation in a riparian zone.

    PubMed

    Borden, Robert C; Knox, Sheri L; Lieberman, M Tony; Ogles, Dora

    2014-01-01

    Multiple lines of evidence were used to document the natural attenuation of perchlorate in a shallow alluvial aquifer. In the upgradient, aerobic portion of the aquifer, perchlorate did not biodegrade. However, natural flushing by groundwater flow is reducing perchlorate concentrations in the aquifer over time. Perchlorate concentrations in the source area are expected to meet cleanup criteria in 11 to 27 years without active remedial measures. At the distal end of the plume, perchlorate is rapidly degraded as it migrates upward through organic rich littoral zone sediments. Apparent first-order degradation rates in groundwater were about 0.20 d(-1) and are consistent with laboratory macrocosm rates (0.12 d(-1)). qPCR results show a distinct region of the littoral zone where perchlorate degraders are elevated. The Eh within this zone varies from +0.1 to +0.3 V indicating perchlorate degraders can thrive in moderately oxidizing conditions. The study has shown that (i) there was no apparent perchlorate biodegradation in aerobic aquifer; (ii) perchlorate declines over time in aerobic aquifer due to flushing; (iii) there was a rapid perchlorate attenuation in organic rich littoral zone; and, (iv) qPCR results show large increases in perchlorate degraders in the littoral zone.

  16. Attenuation of coda waves in northern Greece

    NASA Astrophysics Data System (ADS)

    Hatzidimitriou, P. M.

    1993-03-01

    The single scattering model has been applied for the estimation of coda Q values for local earthquakes that occurred in northern Greece during the period 1983 1989 and recorded by the telemetered network of the Geophysical Laboratory of the University of Thessaloniki. Coda Q estimations were made for four frequency bands centered at 1.5 Hz, 3.0 Hz, 6.0 Hz and 12.0 Hz and for the lapse time windows 10 20 sec, 15 30 sec, 20 45 sec, 30 60 sec and 50 100 sec. The coda Q values obtained show a clear frequency dependence of the form Q c =Q 0 f n , while Q 0 and n depend on the lapse time window. Q 0 was found equal to 33 and n equal to 1.01 for the time window of 10 to 20 sec, while for the other windows Q 0 increased from 60 to 129, with n being stable, close to 0.75. This lapse time dependence is interpreted as due to a depth dependent attenuation. The high attenuation and the strong frequency dependence found are characteristic of an area with high seismicity, in agreement with studies in other seismic regions.

  17. A low-reflection coaxial tunable attenuator based on zero refractive index metamaterial

    NASA Astrophysics Data System (ADS)

    Zhang, Kai-Lun; Hou, Zhi-Ling; Wang, Chan-Yuan; Kong, Ling-Bao; Bian, Xin-Ming

    2016-11-01

    In this paper, we design a low-reflection coaxial tunable attenuator with a maximum attenuation of -50 dB by use of zero refractive index metamaterial. Almost no reflection is observed from input port of the proposed structure, due to the easily accessible impedance matching derived from the use of zero refractive index metamaterial. The relationship between attenuation and the air gap width can be well described by an equivalent circuit model. Interestingly, the ratio of input to output voltage is linearly related to the gap width due to the eliminated fringing capacitance by zero-refraction metamaterial, which makes it easy to achieve accurate calibration of the proposed attenuator. The low reflection and linear relationships enable the proposed attenuator to hold promising potential for practical applications.

  18. 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.

  19. On Corner Frequencies, Attenuation and Low-Frequency Earthquakes

    NASA Astrophysics Data System (ADS)

    Bostock, M. G.; Thomas, A.; Rubin, A. M.; Christensen, N. I.

    2016-12-01

    Characterization of earthquake sources is often performed by parametric modelling of particle displacement seismograms in the log-log spectral domain where the low-frequency, horizontal asymptote yields seismic moment and the intersection of low- and high-frequency asymptotes defines corner frequency, a measure of rupture duration from which source dimension and stress drop can be inferred. The latter definition of corner frequency, though practical and in widespread use, is less convenient for analytic purposes. We employ an alternate definition of corner frequency in the context of standard parametric models as the frequency at which the particle velocity spectrum attains its maximum, to examine the effect of attenuation in biassing corner frequency measurements. This approach indicates that, for a given path and attenuation model, there exists a maximum ``saturation'' frequency that can be observed, as true corner frequency tends to infinity. Equivalently, one may set a minimum bound on path averaged Q from an observed apparent corner frequency. We apply these relations to deep crustal and intraplate seismicity beneath Vancouver Island to estimate bulk crustal attenuation parameters that are subsequently used to correct apparent corner frequency measurements of low frequency earthquakes reported in a previous study. The attenuation bias due to bulk crustal structure is shown to be small, with negligible effect on the principal conclusions of that study. However, evidence for high P-to-S LFE corner frequency ratios raises the possibility that strong, localized, near-source attenuation accompanying high pore-fluid pressures governs the peculiar spectral properties of LFEs.

  20. 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. © 2015 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.

  1. 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.

  2. Determining Source Attenuation History to Support Closure by Natural Attenuation

    DTIC Science & Technology

    2013-11-01

    Low k zone (clay) k interface High k zone (sand) Interval w/ highest contaminant levels ( approximate ) MIP (continuous data) Geoprobe HPT (continuous...reflective of long - term trends. Furthermore, regulators frequently adhere to a conceptual model of an unchanging, non- attenuating source zone, and...especially as subsurface releases age over time. To aid in the selection of MNA as a long - term remedy, we propose a new approach that allows for

  3. The Gas Flow from the Gas Attenuator to the Beam Line

    SciTech Connect

    Ryutov, D.D.

    2010-12-03

    The gas leak from the gas attenuator to the main beam line of the Linac Coherent Light Source has been evaluated, with the effect of the Knudsen molecular beam included. It has been found that the gas leak from the gas attenuator of the present design, with nitrogen as a working gas, does not exceed 10{sup -5} torr x l/s even at the highest pressure in the main attenuation cell (20 torr).

  4. 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.

  5. 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

  6. 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. Copyright © 2015 Elsevier Inc. All rights reserved.

  7. 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).

  8. Ultrasound fields in attenuating media.

    PubMed

    Lerch, R; Friedrich, W

    1986-10-01

    For medical ultrasonic imaging and for nondestructive testing, the attenuation of pressure waves and the resulting shift in wave velocity are important features in commonly used transmission media such as biological tissue. An algorithm for the numerical evaluation of pressure field distributions generated by ultrasonic transducers is presented. The attenuation and dispersion of the sound transmission medium are taken into consideration. The sound fields are computed numerically for continuous wave as well as pulse excitation. The transducer has plane or gently curved geometry and is embedded in a plane rigid baffle. The numerically determined pressure fields are presented as 3D plots, as gray-scale images for a fixed time stamp (like a snapshot), or as isobars regarding the maximum values over time for each local point in the area under investigation. The algorithm described here can be utilized as a tool for design of ultrasound transducers, especially array antennas.

  9. Lg wave attenuation in Britain

    NASA Astrophysics Data System (ADS)

    Sargeant, Susanne; Ottemöller, Lars

    2009-12-01

    The Lg wave quality factor (QLg) in Britain has been modelled using data from the UK Seismic Network, operated by the British Geological Survey. The data set consists of 631 vertical, mostly short-period recordings of Lg waves from 64 earthquakes (2.7-4.7 ML) and 93 stations. We have inverted for both regional average QLg and tomographic images of QLg, and simultaneously a source term for each event and a site term for each station for 22 frequencies in the band 0.9-10.0 Hz. The regional average model is 266f0.53 between 1.0 and 10.0 Hz and indicates that attenuation in Britain is slightly higher than in France, and significantly higher than in eastern North America and Scandinavia. Tomographic inversions at each frequency indicate that QLg varies spatially. Broadly speaking, southeastern England, the Lake District and parts of the East Irish Sea Basin, and a small region between the Highland Boundary Fault and the Southern Uplands Fault are characterized by higher than average attenuation. Southwestern England, eastern central England and northwestern Scotland are regions of relatively low attenuation. To some extent, these regions correlate with what is known about the tectonics and structure of the crust in the UK.

  10. Satellite Microwave Communication Signal Degradation Due To Hall Thruster Plasma Plumes

    NASA Astrophysics Data System (ADS)

    Wiley, J. C.; Hallock, G. A.; Spencer, E. A.; Meyer, J. W.; Loane, J. T.

    2001-10-01

    We have developed a geometric optics vector ray-tracing code, BeamServer, for analyzing the effects of Hall thruster plasma plumes on satellite microwave communication signals. The possible effects include main beam attenuation and squinting, side lobe degradation, and induced cross-polarization. We report on a study of Hall current thruster (HCT) mounting positions on a realistic satellite configuration and a study with a highly shaped reflector. Results indicate HCT signal degradation can occur and should be considered in the satellite design process. Initial results of antenna pattern perturbations due to low frequency plume oscillations driven by thruster instabilities are also given.

  11. 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.

  12. Effects of elastic focusing on global models of Rayleigh wave attenuation

    NASA Astrophysics Data System (ADS)

    Bao, Xueyang; Dalton, Colleen A.; Ritsema, Jeroen

    2016-11-01

    Rayleigh wave amplitudes are the primary data set used for imaging shear attenuation in the upper mantle on a global scale. In addition to attenuation, surface-wave amplitudes are influenced by excitation at the earthquake source, focusing and scattering by elastic heterogeneity, and local structure at the receiver and the instrument response. The challenge of isolating the signal of attenuation from these other effects limits both the resolution of global attenuation models and the level of consistency between different global attenuation studies. While the source and receiver terms can be estimated using relatively simple approaches, focusing effects on amplitude are a large component of the amplitude signal and are sensitive to multiscale velocity anomalies. In this study we investigate how different theoretical treatments for focusing effects on Rayleigh wave amplitude influence the retrieved attenuation models. A new data set of fundamental-mode Rayleigh wave phase and amplitude at periods of 50 and 100 sis analysed. The amplitudes due to focusing effects are predicted using the great-circle ray approximation (GCRA), exact ray theory (ERT), and finite-frequency theory (FFT). Phase-velocity maps expanded to spherical-harmonic degree 20 and degree 40 are used for the predictions. After correction for focusing effects, the amplitude data are inverted for global attenuation maps and frequency-dependent source and receiver correction factors. The degree-12 attenuation maps, based on different corrections for focusing effects, all contain the same large-scale features, though the magnitude of the attenuation variations depends on the focusing correction. The variance reduction of the amplitudes strongly depends on the predicted focusing amplitudes, with the highest variance reduction for the ray-based approaches at 50 s and for FFT at 100 s. Although failure to account for focusing effects introduces artefacts into the attenuation models at higher spherical

  13. MLAA-based RF surface coil attenuation estimation in hybrid PET/MR imaging

    NASA Astrophysics Data System (ADS)

    Heußer, Thorsten; Rank, Christopher M.; Freitag, Martin T.; Kachelrieß, Marc

    2017-03-01

    Attenuation correction (AC) for both patient and hardware attenuation of the 511 keV annihilation photons is required for accurate PET quantification. In hybrid PET/MR imaging, AC for stationary hardware components such as patient table and MR head coil is performed using CT{derived attenuation templates. AC for flexible hardware components such as MR radiofrequency (RF) surface coils is more challenging. Registration{based approaches, aligning scaled CT{derived attenuation templates with the current patient position, have been proposed but are not used in clinical routine. Ignoring RF coil attenuation has been shown to result in regional activity underestimation values of up to 18 %. We propose to employ a modified version of the maximum{ likelihood reconstruction of attenuation and activity (MLAA) algorithm to obtain an estimate of the RF coil attenuation. Starting with an initial attenuation map not including the RF coil, the attenuation update of MLAA is applied outside the body outline only, allowing to estimate RF coil attenuation without changing the patient attenuation map. Hence, the proposed method is referred to as external MLAA (xMLAA). In this work, xMLAA for RF surface coil attenuation estimation is investigated using phantom and patient data acquired with a Siemens Biograph mMR. For the phantom data, average activity errors compared to the ground truth was reduced from -8:1% to +0:8% when using the proposed method. Patient data revealed an average activity underestimation of -6:1% for the abdominal region and -5:3% for the thoracic region when ignoring RF coil attenuation.

  14. 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

  15. 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.

  16. 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

  17. 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.

  18. Attenuation tomography of the upper mantle

    NASA Astrophysics Data System (ADS)

    Adenis, Alice; Debayle, Eric; Ricard, Yanick

    2017-08-01

    We present QsADR17, a global shear wave attenuation model of the upper mantle. Synthetic tests confirm that large-scale shear attenuation anomalies are resolved in the whole upper mantle with limited vertical smearing (≤50 km). QsADR17 shows strong correlation with surface tectonics down to 200 km depth, with low attenuation beneath continents and high attenuation beneath oceans. The attenuation signal near 250 km depth is dominated by a high-quality factor along subduction zones. Attenuating anomalies are found beneath mid-ocean ridges down to 150 km and under most Pacific hot spots from the lithosphere down to the transition zone. The presence of broad attenuating anomalies at 150 km depth in the Pacific Ocean suggests that several thermal plumes pond in the asthenosphere. Evidence for compositional heterogeneities is found in the lithosphere at the base of cratons and in a number of active regions.

  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. On corner frequencies, attenuation, and low-frequency earthquakes

    NASA Astrophysics Data System (ADS)

    Bostock, M. G.; Thomas, A. M.; Rubin, A. M.; Christensen, N. I.

    2017-01-01

    We have recently suggested that the nearly constant duration of low-frequency earthquakes (LFEs) (and, equivalently, the band limitation of tectonic tremor) manifests a moment-duration scaling that is fundamentally different from regular earthquakes and is most easily explained as rupture on asperities of roughly constant dimension. In that work, we employed qualitative arguments against potential bias by attenuation. Here we examine the role of attenuation more quantitatively through an analysis that avoids specification of particular source (e.g., Brune) models and relies on the particle velocity spectral maximum as the definition of apparent corner frequency. The analysis leads to the formal definition of a saturation frequency as the limiting value of apparent corner frequency as the true corner frequency tends infinity. The saturation frequency, a formal equivalent to fmax, can be used to set bounds on path-averaged quality factor Q. We apply these relations to deep crustal and intraslab earthquakes beneath Vancouver Island to estimate bulk crustal attenuation parameters that are subsequently used to correct apparent corner frequency measurements of LFEs reported in our earlier work. The attenuation bias due to bulk crustal structure is shown to be small, with negligible effect on the principal conclusions of that study. However, a review of laboratory and seismic refraction measurements of attenuation in oceanic basalts and evidence for high P-to-S LFE corner frequency ratios raises the possibility that strong, highly localized, near-source attenuation accompanying high pore-fluid pressures could cause the bandlimited nature of LFEs through the depletion of high frequencies.

  1. Attenuation of polychlorinated biphenyl sorption to charcoal by humic acids.

    PubMed

    Koelmans, Albert A; Meulman, Brendo; Meijer, Thijs; Jonker, Michiel T O

    2009-02-01

    Strong sorption to black carbon may limit the environmental risks of organic pollutants, but interactions with cosorbing humic acid (HA) may interfere. We studied the attenuative effect of HA additions on the sorption of polychlorinated biphenyls (PCBs) to a charcoal. "Intrinsic" sorption to HA-amended charcoal was calculated by subtracting the sorption contribution of HA from the total sorption to charcoal and HA. Association of PCBs with HA was proportional to hydrophobicity. However, the planar PCBs 77 and 126 had an additional 2-4 times stronger association than expected from hydrophobicity alone. Sorption isotherms for the raw charcoal fitted slightly better to a three-parameter Polanyi-Dubinin-Manes model than to a two-parameter Langmuir model. Preloading the charcoal with 1-75 mg of HA/g of charcoal increasingly attenuated sorption to charcoal with up to a factor of 10. The resultant isotherms could be described adequately with the Freundlich model. Isotherm nonlinearity increased with HA loading, suggesting increased sorption competition between HA and PCBs. Attenuation was negligible in the PCB picogram per liter to nanogram per liter range and increased at higher PCB concentrations, which points to saturation of binding sites on the charcoal. Attenuation was highest for planar congeners, which suggests an additional site blockage mechanism. These variations due to HA loading and PCB concentration can explain the variability in attenuation reported in earlier work and imply that the use of constant "attenuation factors" to adjust sorption coefficients determined for pure carbonaceous materials in order to apply them to field situations may not be warranted.

  2. Attenuation correction in molecular fluorescence imaging (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Yang, Bin; Tunnell, James W.

    2016-03-01

    Fluorescence-guided surgery has demonstrated more complete tumor resections in both preclinical models and clinical applications. However, intraoperative fluorescence-based imaging can be challenging due to attenuation of the fluorescence by intrinsic tissue scattering and absorption. Removing attenuation in fluorescence imaging is critical in many applications. We have developed both a model based approach and an experimental approach to retrieve attenuation corrected fluorescence based on spatial frequency domain imaging (SFDI). In the model based approach, we extended an attenuation correction model initially developed for point measurement into wide-field imaging with SFDI. To achieve attenuation correction, tissue optical properties were evaluated at both excitation and emission wavelengths, which were later applied in the model. In an in-vitro phantom study, we achieved a relative flat intensity profile over entire absorption range compared to over 80% drop at the highest absorption level before correction. Similar performance was also observed in an ex-vivo tissue study. However, lengthy image acquisition and image processing make this method ideal for static imaging instead of video-rate imaging. To achieve video-rate correction, we developed an experimental approach to reduce absorption by limiting the imaging depth using a high spatial frequency pattern. The absorption reduced fluorescence image was obtained by performing a simple demodulation. The in-vitro phantom study suggested an approximate 20% intensity drop at the highest absorption level compared to over 70% intensity drop before correction. This approach enabled video-rate attenuation corrected imaging at 19 fps, making this technique viable for clinical image guided surgery.

  3. Metabolic Bone Disease in the Context of Metastatic Neuroendocrine Tumor: Differentiation from Skeletal Metastasis, the Molecular PET–CT Imaging Features, and Exploring the Possible Etiopathologies Including Parathyroid Adenoma (MEN1) and Paraneoplastic Humoral Hypercalcemia of Malignancy Due to PTHrP Hypersecretion

    PubMed Central

    Ranade, Rohit; Basu, Sandip

    2017-01-01

    Three cases of metabolic bone disease in the setting of metastatic neuroendocrine tumor (NET) are illustrated with associated etiopathologies.  One of these cases harbored mixed lesions in the form of vertebral metastasis (biopsy proven) while the other skeletal lesions were caused due to metabolic bone disease related to multiple parathyroid adenomas. While the metastatic lesion was positive on 68Ga-DOTATATE positron emission tomography-computed tomography (PET-CT), the lesions of metabolic bone disease were negative and the 18F-fluoride PET-CT demonstrated the features of metabolic bone scan. Similar picture of metabolic bone disease [18-sodium fluoride (18NaF)/68Ga-DOTATATE mismatch] was documented in the other two patients, while fluorodeoxyglucose (FDG)-PET-CT was variably positive, primarily showing tracer uptake in the metabolic skeletal lesions of the patient with hypersecretion of parathyroid hormone-related protein (PTHrP) by the underlying tumor. Discordance between 18NaF PET-CT and 68Ga-DOTATATE PET-CT serves as a good marker for identification of metabolic bone disease and diagnosing such a clinical entity. In a patient of NET with metabolic bone disease and hypercalcemia, thus, two causes need to be considered: (i) Coexisting parathyroid adenoma in multiple endocrine neoplasia type I (MEN-I) syndrome and (ii) humoral hypercalcemia of malignancy (HHM) related to hypersecretion of PTHrP by the tumor. The correct diagnosis of metabolic bone disease in metastatic NET can alter the management substantially. Interestingly, peptide receptor radionuclide therapy (PRRT) can emerge as a very promising treatment modality in patients of metabolic bone disease caused by HHM in the setting of NET. PMID:28217023

  4. Influence of attenuation on radionuclide stroke volume determinations

    SciTech Connect

    Burow, R.D.; Wilson, M.F.; Heath, P.W.; Corn, C.R.; Amil, A.; Thadani, U.

    1982-09-01

    Using a method for determination of absolute volumes, including correcting for attenuation, we have explored the ability of the method to determine stroke volume in humans by radionuclide techniques. Thermodilution cardiac output determinations and multigated equilibrium blood-pool scintigraphy in the LAO view were performed simultaneously in twenty patients in which no evidence of intracardiac shunts or valvular disease was present. The correlation was good between the attenuated radionuclide and thermodilution stroke volume (r . 0.80, s.e.e. of estimate . 12 ml; SVtd . 2.31 x SVr + 18 ml). When correction for attenuation was made, the correlation improved (r . 0.96, s.e.e. . 6 ml) and approached the line of identity (SVtd . 0.99 x SVr + 1.2 ml). The correlation was also good between radionuclide cardiac output, corrected for attenuation, and the thermodilution cardiac output (r . 0.89, s.e.e. . 0.36 l/min; COtd . 0.86 x COr + 0.67 l/min). Thus our method of correction for attenuation in the determination of absolute left-ventricular volumes has been shown to provide a reliable, noninvasive means of calculating stroke volume and cardiac output in humans, without the use of geometric assumptions or regression equations.

  5. 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.

  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. 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.

  8. Mode-dependent attenuation of optical fibers: excess loss.

    PubMed

    Olshansky, R; Nolan, D A

    1976-04-01

    A theory is presented for calculating the excess loss produced by random perturbations of optical fibers. The theory is applicable to perturbations whose longitudinal spatial frequencies are below the range required for mode coupling. To illustrate the method, losses due to diameter variations are calculated for the case of a step-index optical fiber. The diameter variations are found to produce a strong attenuation of the higher order modes. The total excess loss is approximately wavelength independent.

  9. 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.

  10. A description of shock attenuation for children running.

    PubMed

    Mercer, John A; Dufek, Janet S; Mangus, Brent C; Rubley, Mack D; Bhanot, Kunal; Aldridge, Jennifer M

    2010-01-01

    A growing number of children are participating in organized sport activities, resulting in a concomitant increase in lower extremity injuries. Little is known about the impact generated when children are running or how this impact is attenuated in child runners. To describe shock attenuation characteristics for children running at different speeds on a treadmill and at a single speed over ground. Prospective cohort study. Biomechanics laboratory. Eleven boys (age = 10.5 +/- 0.9 years, height = 143.7 +/- 8.3 cm, mass = 39.4 +/- 10.9 kg) and 7 girls (age = 9.9 +/- 1.1 years, height = 136.2 +/- 7.7 cm, mass = 35.1 +/- 9.6 kg) participated. Participants completed 4 running conditions, including 3 treadmill (TM) running speeds (preferred, fast [0.5 m/s more than preferred], and slow [0.5 m/s less than preferred]) and 1 overground (OG) running speed. We measured leg peak impact acceleration (LgPk), head peak impact acceleration (HdPk), and shock attenuation (ratio of LgPk to HdPk). Shock attenuation (F(2,16) = 4.80, P = .01) was influenced by the interaction of speed and sex. Shock attenuation increased across speeds (slow, preferred, fast) for boys (P < .05) but not for girls (P > .05). Both LgPk (F(1,16) = 5.04, P = .04) and HdPk (F(1,16) = 6.04, P = .03) were different across speeds, and both were greater for girls than for boys. None of the dependent variables were influenced by the interaction of setting (TM, OG) and sex (P >or= .05). Shock attenuation (F(1,16) = 33.51, P < .001) and LgPk (F(1,16) = 31.54, P < .001) were different between TM and OG, and each was greater when running OG than on the TM, regardless of sex. Shock attenuation was between 66% and 76% for children running under a variety of conditions. Girls had greater peak impact accelerations at the leg and head levels than boys but achieved similar shock attenuation. We do not know how these shock attenuation characteristics are related to overuse injuries.

  11. 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.

  12. A Global Upper-Mantle Tomographic Model of Shear Attenuation

    NASA Astrophysics Data System (ADS)

    Karaoglu, H.; Romanowicz, B. A.

    2016-12-01

    Mapping anelastic 3D structure within the earth's mantle is key to understanding present day mantle dynamics, as it provides complementary constraints to those obtained from elastic structure, with the potential to distinguish between thermal and compositional heterogeneity. For this, we need to measure seismic wave amplitudes, which are sensitive to both elastic (through focusing and scattering) and anelastic structure. The elastic effects are less pronounced at long periods, so previous global upper-mantle attenuation models are based on teleseismic surface wave data, sometimes including overtones. In these studies, elastic effects are considered either indirectly, by eliminating data strongly contaminated by them (e.g. Romanowicz, 1995; Gung and Romanowicz, 2004), or by correcting for elastic focusing effects using an approximate linear approach (Dalton et al., 2008). Additionally, in these studies, the elastic structure is held fixed when inverting for intrinsic attenuation . The importance of (1) having a good starting elastic model, (2) accurate modeling of the seismic wavefield and (3) joint inversion for elastic and anelastic structure, becomes more evident as the targeted resolution level increases. Also, velocity dispersion effects due to anelasticity need to be taken into account. Here, we employ a hybrid full waveform inversion method, inverting jointly for global elastic and anelastic upper mantle structure, starting from the latest global 3D shear velocity model built by our group (French and Romanowicz, 2014), using the spectral element method for the forward waveform modeling (Capdeville et al., 2003), and normal-mode perturbation theory (NACT - Li and Romanowicz, 1995) for kernel computations. We present a 3D upper-mantle anelastic model built by using three component fundamental and overtone surface waveforms down to 60 s as well as long period body waveforms down to 30 s. We also include source and site effects to first order as frequency

  13. The evaluation of natural attenuation processes in ecological risk assessments

    SciTech Connect

    Swindoll, C.M.; Dziuk, L.J. |

    1994-12-31

    The intent of the ecological risk assessment (ERA) process is to provide the scientific basis for making remediation decisions that are protective of the environment. In some instances, remedial actions may result in more damage to area flora and fauna than is warranted based on the long-term risk of the chemical stressor; this is particularly true of wetlands. To minimize the potential for putting the site`s ecosystem at greater risk because of remediation, the ERA should include an evaluation of ``no action`` and ``nondestructive`` scenarios. An essential component of this evaluation is an assessment of the natural attenuation of the chemical stressor. Natural processes including biodegradation, hydrolysis, photodegradation, speciation, and complexation can be important to the mitigation of long-term ecological impact of chemical substances. The importance of natural processes for the attenuation of contaminants in aquifers is recognized by both the regulatory and scientific communities and has been adopted by several states as a viable remedial alternative. The potential for natural attenuation to reduce environmental risk is greater for surface environments than for the subsurface. The rationale, methodology, and tools available for evaluating natural attenuation in the context of the ERA process will be presented. Specific examples of implementing this approach at several industrial sites and benefits, including the effective utilization of limited regulatory and industrial resources, will be discussed.

  14. Experimental study of seismic attenuation in partially saturated porous media

    NASA Astrophysics Data System (ADS)

    Barrière, Julien; Bordes, Clarisse; Sénéchal, Pascale

    2010-05-01

    Nowadays, it is well admitted that hydrogeological properties of the porous media (porosity, fluid saturation and permeability) can influence seismic properties. In geophysics, the major theory which links hydrogeological and seismic parameters is poroelasticity proposed by Biot (1956). The Biot relaxation process is due to the relative displacement of fluid in comparison to the solid which causes a significant attenuation of seismic waves, notably in unconsolidated medium. In partially saturated medium, pore fluids are considered as a perfect mixture and so called 'effective fluid'. However, in more consolidated rocks, the Biot theory is not sufficient to explain the attenuation level as measured from field seismic and sonic log data. In the last decade, some authors provide new theories to understand the attenuation caused by the interaction of the different fluids. Most experiments are done in the ultrasonic frequency range, where sources of attenuation (like scattering or local fluid flow) are different as in the low frequency range where the wavelength is greater than heterogeneities size. In this way, we propose a forward-looking experiment with the use of a vertical impulsionnal seismic source which have a strong amplitude spectrum ranging from 100Hz to 8kHz. We study three different unconsolidated porous media at atmospheric pressure: fine-grained sand, coarsed-grained sand and coarse gravel. Water content is measured with a calibrated capacitance probe and temperature effects are corrected. Seismic wave propagation is recorded by piezoelectric accelerometers designed for frequencies below 10kHz. The water injection is done by imbibition. We propose to analyse the attenuation in the [100Hz-1.5kHz] frequency range for the studied media with various water saturation levels. The attenuation varies according to the porous medium and the water content and appears more significant at dry condition and at high saturation level. The weak cohesion at dry condition

  15. 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.

  16. 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. Copyright © 2012 Elsevier Ltd. All rights reserved.

  17. Studies on Shock Attenuation in Plastic Materials and Applications in Detonation Wave Shaping

    NASA Astrophysics Data System (ADS)

    Khurana, Ritu; Gautam, P. C.; Rai, Rajwant; Kumar, Anil; Sharma, A. C.; Singh, Manjit, Dr

    2012-07-01

    Pressure in plastic materials attenuates due to change of impedance, phase change in the medium and plastic deformation. A lot of theoretical and experimental efforts have been devoted to the attenuation of shock wave produced by the impact of explosive driven flyer plate. However comparatively less work has been done on the attenuation of shock waves due to contact explosive detonation. Present studies deal with the attenuation of explosive driven shock waves in various plastic materials and its applications in design of Hybrid Detonation Wave Generator In present work shock attenuating properties of different polymers such as Perspex, Teflon, nylon, polypropylene and viton has been studied experimentally using rotating mirror streak camera and electrical position pins. High explosive RDX/TNT and OCTOL of diameter 75-100mm and thickness 20 to 50mm were detonated to induce shock wave in the test specimens. From experimental determined shock velocity at different locations the attenuation in shock pressure was calculated. The attenuation of shock velocity with thickness in the material indicates exponential decay according to relation US = UOexp(-ax). In few of the experiments manganin gauge of resistance 50 ohms was used to record stress time profile across shock wave. The shock attenuation data of Viton has successfully been used in the design of hybrid detonation wave generator using Octol as high explosive. While selecting a material it was ensured that the attenuated shock remains strong enough to initiate an acceptor explosive. Theoretical calculation were supported by Autodyne 2D hydro-code simulation which were validated with the experiments conducted using high speed streak photography and electrical shock arrival pins. Shock attenuation data of Perspex was used to establishing card gap test and wedge test in which test items is subjected to known pressure pulse by selecting the thickness of the plastic material.

  18. In vitro measurement of attenuation and nonlinear scattering from echogenic liposomes.

    PubMed

    Paul, Shirshendu; Russakow, Daniel; Nahire, Rahul; Nandy, Tapas; Ambre, Avinash H; Katti, Kalpana; Mallik, Sanku; Sarkar, Kausik

    2012-09-01

    Echogenic liposomes (ELIP) are an excellent candidate for concurrent imaging and drug delivery applications. They combine the advantages of liposomes-biocompatibility and ability to encapsulate both hydrophobic and hydrophilic drugs-with strong reflections of ultrasound. The objective of this study is to perform a detailed in vitro acoustic characterization - including nonlinear scattering that has not been studied before - along with an investigation of the primary mechanism of echogenicity. Both components are critical for developing viable clinical applications of ELIP. Mannitol, a cryoprotectant, added during the preparation of ELIP is commonly believed to be critical in making them echogenic. Accordingly, here ELIP prepared with varying amount of mannitol concentration are investigated for their pressure dependent linear and non-linear scattered responses. The average diameter of these liposomes is measured to be 125-185nm. But they have a broad size distribution including liposomes with diameters over a micro-meter as observed by TEM and AFM. These larger liposomes are critical for the overall echogenicity. Attenuation through liposomal solution is measured with four different transducers (central frequencies 2.25, 3.5, 5, 10MHz). Measured attenuation increases linearly with liposome concentration indicating absence of acoustic interactions between liposomes. Due to the broad size distribution, the attenuation shows a flat response without a distinct peak in the range of frequencies (1-12MHz) investigated. A 15-20dB enhancement with 1.67 μg/ml of lipids is observed both for the scattered fundamental and the second harmonic responses at 3.5MHz excitation frequency and 50-800kPa amplitude. It demonstrates the efficacy of ELIP for fundamental as well as harmonic ultrasound imaging. The scattered response however does not show any distinct subharmonic peak for the acoustic excitation parameters studied. Small amount of mannitol proves critical for echogenicity

  19. Investigation of the use of X-ray CT images for attenuation compensation in SPECT

    SciTech Connect

    LaCroix, K.J.; Tsui, B.M.W. ); Hasegawa, B.H.; Brown, J.K. )

    1994-12-01

    This study investigates the general use of single-beam X-ray computed tomography (CT) images for generating attenuation maps for compensation of photon attenuation in SPECT images. A 3D mathematical thorax phantom is used to simulate both emission and transmission projection data for monoenergetic and polyenergetic sources. Polyenergetic transmission projection data are simulated for a standard X-ray spectrum and fan-beam geometry. The projection data are reconstructed using filtered backprojection to form an X-ray CT image which is then scaled to produce an estimate of the attenuation map at the energy of the emission radionuclide. Emission projection data are simulated for a fan-beam geometry at the energies of [sup 201]Tl and [sup 99m]Tc, two radionuclides commonly used in cardiac SPECT. Detector response and scatter are not included in the model. Noiseless, emission projection data are iteratively reconstructed using the ML-EM algorithm with nonuniform attenuation compensation and attenuation maps derived from both the simulated X-ray CT image and from a simulated monoenergetic transmission CT image. The attenuation maps generated from the X-ray CT images accurately estimate the attenuation coefficient for muscle and lung tissues, but not for bone tissues, which show error in the attenuation coefficient of 21--42% for spinal bone and 34--58% for rib bone. However, despite the inaccurate estimate of bone attenuation, the reconstructed SPECT images provide estimates of myocardial radioactivity concentration to within 9% and show few artifacts.

  20. Body Wave Crustal Attenuation Characteristics in the Garhwal Himalaya, India

    NASA Astrophysics Data System (ADS)

    Negi, Sanjay S.; Paul, Ajay; Joshi, Anand; Kamal

    2015-06-01

    We estimate frequency-dependent attenuation of P and S waves in Garhwal Himalaya using the extended coda normalization method for the central frequencies 1.5, 2, 3, 4, 6, 8, 10, 12, and 16 Hz, with earthquake hypocentral distance ranging from 27 to 200 km. Forty well-located local earthquake waveforms were used to study the seismic attenuation characteristics of the Garhwal Himalaya, India, as recorded by eight stations operated by Wadia Institute of Himalayan Geology, Dehradun, India, from 2007 to 2012. We find frequency-dependent P and S wave quality factors as defined by the relations Q P = 56 ± 8 f 0.91±0.002 and Q S = 151 ± 8 f 0.84±0.002 by fitting a power-law frequency dependence model for the estimated values over the whole region. Both the Q P and Q S values indicate strong attenuation in the crust of Garhwal Himalaya. The ratio of Q S/ Q P > 1 obtained for the entire analyzed frequency range suggests that the scattering loss is due to a random and high degree of heterogeneities in the earth medium, playing an important role in seismic wave attenuation in the Himalayan crust.

  1. Interpersonal sensitivity and persistent attenuated psychotic symptoms in adolescence.

    PubMed

    Masillo, Alice; Brandizzi, M; Valmaggia, L R; Saba, R; Lo Cascio, N; Lindau, J F; Telesforo, L; Venturini, P; Montanaro, D; Di Pietro, D; D'Alema, M; Girardi, P; Fiori Nastro, P

    2017-09-16

    Interpersonal sensitivity defines feelings of inner-fragility in the presence of others due to the expectation of criticism or rejection. Interpersonal sensitivity was found to be related to attenuated positive psychotic symptom during the prodromal phase of psychosis. The aims of this study were to examine if high level of interpersonal sensitivity at baseline are associated with the persistence of attenuated positive psychotic symptoms and general psychopathology at 18-month follow-up. A sample of 85 help-seeking individuals (mean age = 16.6, SD = 5.05) referred an Italian early detection project, completed the interpersonal sensitivity measure and the structured interview for prodromal symptoms (SIPS) at baseline and were assessed at 18-month follow-up using the SIPS. Results showed that individuals with high level of interpersonal sensitivity at baseline reported high level of attenuated positive psychotic symptoms (i.e., unusual thought content) and general symptoms (i.e., depression, irritability and low tolerance to daily stress) at follow-up. This study suggests that being "hypersensitive" to interpersonal interactions is a psychological feature associated with attenuated positive psychotic symptoms and general symptoms, such as depression and irritability, at 18-month follow-up. Assessing and treating inner-self fragilities may be an important step of early detection program to avoid the persistence of subtle but very distressing long-terms symptoms.

  2. Rg propagation: Scatter versus Attenuation

    NASA Astrophysics Data System (ADS)

    Cleveland, M.; Phillips, W. S.; MacCarthy, J.

    2016-12-01

    At near local distances, the Rg seismic phase is often the largest seismic arrival for shallow sources. While Rg is classically defined for the period range of 8-12 s, we use the term generically to refer to short-period observations of Rayleigh waves from shallow sources [e.g. Langston, 1987; Bonner and Russell, 2013]. There is significant interest in using Rg as a basis for seismic discrimination and magnitude (e.g. Bonner and Russell, 2013). However, the propagation of this phase is poorly understood. At Nevada National Security Site, while Rg is well observed near the source, it quickly disappears at greater distances. This observation raises the fundamental question of how much of the Rg energy is simply attenuating versus scattering into other seismic phases. Understanding this is critical to interpreting not only the observed Rg seismic energy, but also the possible enrichment of other seismic phases resulting from Rg scattering. In this study, we use waveform data from the Bighorn Arch Seismic Experiment (BASE) and Source Physics Experiment (SPE) to investigate Rg propagation, looking to identify how much energy from the phase attenuates with distance and how much scatters into other seismic phases.

  3. 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

  4. Individual effects of stride length and frequency on shock attenuation during running.

    PubMed

    Mercer, John A; Devita, Paul; Derrick, Tim R; Bates, Barry T

    2003-02-01

    Shock attenuation during running is the process of absorbing impact energy due to the foot-ground collision, reducing shock wave amplitude between the foot and head. Shock attenuation is affected by changes in stride length and stride frequency, but it is not clear whether either parameter individually affects shock attenuation. To identify the independent affects of stride length (SL) and stride frequency (SF) on shock attenuation. Subjects ( N = 10) completed three experiments consisting of SL and SF manipulations relative to preferred stride length (PSL) and frequency (PSF). During experiment 1, stride length was manipulated (+15% PSL, PSL, -15% PSL) while stride frequency was always set to PSF. During experiment 2, stride frequency was manipulated (+15% PSF, PSF, -15% PSF) while stride length was always set to PSL. During experiment 3, stride length and stride frequency were manipulated concurrently (+10% PSL/-10% PSF, PSL/PSF, and -10% PSL/+10% PSF). Running velocity was always the product of stride length and stride frequency. Transfer functions were calculated using tibial and forehead surface mounted accelerometer data to represent shock attenuation. Shock attenuation changed only when stride length changed ( P < 0.05). Specifically, shock attenuation increased as stride length increased. It was concluded that changes in stride length not stride frequency affected shock attenuation.

  5. Frequency graded 1D metamaterials: A study on the attenuation bands

    NASA Astrophysics Data System (ADS)

    Banerjee, Arnab; Das, Raj; Calius, Emilio P.

    2017-08-01

    Depending on the frequency, waves can either propagate (transmission band) or be attenuated (attenuation band) while travelling through a one-dimensional spring-mass chain with internal resonators. The literature on wave propagation through a 1D mass-in-mass chain is vast and continues to proliferate because of its versatile applicability in condensed matter physics, optics, chemistry, acoustics, and mechanics. However, in all these areas, a uniformly periodic arrangement of identical linear resonating units is normally used which limits the attenuation band to a narrow frequency range. To counter this limitation of linear uniformly periodic metamaterials, the attenuation bandwidth in a one-dimensional finite chain with frequency graded linear internal resonators are investigated in this paper. The result shows that a properly tuned frequency graded arrangement of resonating units can extend the upper part of the attenuation band of 1D metamaterial theoretically up to infinity and also increases the lower part of the attenuation bandwidth by around 40% of an equivalent uniformly periodic metamaterial without increasing the mass. Therefore, the frequency graded metamaterials can be a potential solution towards low frequency and wideband acoustic or vibration insulation. In addition, this paper provides analytical expressions for the attenuation and transmission frequency limits for a periodic mass-in-mass metamaterial and demonstrates the attenuation band is generated by the high absolute value of the effective mass not only due to the negative effective mass.

  6. 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.

  7. [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.

  8. Due process traditionalism.

    PubMed

    Sunstein, Cass R

    2008-06-01

    In important cases, the Supreme Court has limited the scope of "substantive due process" by reference to tradition, but it has yet to explain why it has done so. Due process traditionalism might be defended in several distinctive ways. The most ambitious defense draws on a set of ideas associated with Edmund Burke and Friedrich Hayek, who suggested that traditions have special credentials by virtue of their acceptance by many minds. But this defense runs into three problems. Those who have participated in a tradition may not have accepted any relevant proposition; they might suffer from a systematic bias; and they might have joined a cascade. An alternative defense sees due process traditionalism as a second-best substitute for two preferable alternatives: a purely procedural approach to the Due Process Clause, and an approach that gives legislatures the benefit of every reasonable doubt. But it is not clear that in these domains, the first-best approaches are especially attractive; and even if they are, the second-best may be an unacceptably crude substitute. The most plausible defense of due process traditionalism operates on rule-consequentialist grounds, with the suggestion that even if traditions are not great, they are often good, and judges do best if they defer to traditions rather than attempting to specify the content of "liberty" on their own. But the rule-consequentialist defense depends on controversial and probably false assumptions about the likely goodness of traditions and the institutional incapacities of judges.

  9. Breast imaging using waveform attenuation tomography

    NASA Astrophysics Data System (ADS)

    Li, Cuiping; Sandhu, Gursharan Y.; Boone, Michael; Duric, Neb

    2017-03-01

    Ex vivo studies using our ultrasound waveform attenuation algorithm have shown promising results for detection and characterization of lesions of different types. Our preliminary in vivo study shows that the waveform attenuation image has much higher resolution and can better delineate breast lesions boundaries than the corresponding ray-based attenuation image. In this study, we preprocessed our time domain waveforms acquired with a ring array and explored the directional transducer beam pattern to better match calculated wave fields with respect to the acquired wave fields. We have applied waveform attenuation to in vivo data and compared the resulting waveform attenuation images with the ray-based counterparts to assess the resolution and accuracy of the waveform attenuation reconstruction.

  10. Identification of an attenuated barley stripe mosaic virus for the virus-induced gene silencing of pathogenesis-related wheat genes.

    PubMed

    Buhrow, Leann M; Clark, Shawn M; Loewen, Michele C

    2016-01-01

    Virus-induced gene silencing (VIGS) has become an emerging technology for the rapid, efficient functional genomic screening of monocot and dicot species. The barley stripe mosaic virus (BSMV) has been described as an effective VIGS vehicle for the evaluation of genes involved in wheat and barley phytopathogenesis; however, these studies have been obscured by BSMV-induced phenotypes and defense responses. The utility of BSMV VIGS may be improved using a BSMV genetic background which is more tolerable to the host plant especially upon secondary infection of highly aggressive, necrotrophic pathogens such as Fusarium graminearum. BSMV-induced VIGS in Triticum aestivum (bread wheat) cv. 'Fielder' was assessed for the study of wheat genes putatively related to Fusarium Head Blight (FHB), the necrotrophism of wheat and other cereals by F. graminearum. Due to the lack of 'Fielder' spike viability and increased accumulation of Fusarium-derived deoxynivalenol contamination upon co-infection of BSMV and FHB, an attenuated BSMV construct was generated by the addition of a glycine-rich, C-terminal peptide to the BSMV γ b protein. This attenuated BSMV effectively silenced target wheat genes while limiting disease severity, deoxynivalenol contamination, and yield loss upon Fusarium co-infection compared to the original BSMV construct. The attenuated BSMV-infected tissue exhibited reduced abscisic, jasmonic, and salicylic acid defense phytohormone accumulation upon secondary Fusarium infection. Finally, the attenuated BSMV was used to investigate the role of the salicylic acid-responsive pathogenesis-related 1 in response to FHB. The use of an attenuated BSMV may be advantageous in characterizing wheat genes involved in phytopathogenesis, including Fusarium necrotrophism, where minimal viral background effects on defense are required. Additionally, the attenuated BSMV elicits reduced defense hormone accumulation, suggesting that this genotype may have applications for the

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Onychomycosis Due to Nondermatophytic Molds

    PubMed Central

    Hwang, Sung Min; Ha, Gyoung Yim

    2012-01-01

    Background Although there have been many studies about onychomycosis due to nondermatophytic molds (NDM), few studies about etiologic agents including NDM in onychomycosis have been reported in Korea. Objective: This study investigated onychomycosis due to NDM in the Gyeongju area of Korea. Objective This study investigated onychomycosis due to NDM in the Gyeongju area of Korea. Methods In the 10-year period from 1999~2009, we reviewed 59 patients with onychomycosis due to NDM. The etiologic agents were identified by cultures on Sabouraud's Dextrose agar with and without cycloheximide. In some cases, internal transcribed spacer sequence analysis was done. NDM isolated considered pathogens when the presence of fungal elements was identified by direct microscopy observation and in follow-up cultures yielding the same fungi. Results Onychomycosis due to NDM comprised 2.3% of all onychomycosis. Of the 59 patients with onychomycosis due to NDM, 84.7% were toenail onychomycosis and 15.3% were fingernail onychomycosis. The incidence rate was highest in the fifth decade (27.1%). The ratio of male to female patients was 1:1.6. The frequency of associated diseases, in descending order, was hypertension, diabetes mellitus, and cerebral hematoma. Distal and lateral subungual onychomycosis (86.4%) was the most common clinical type of onychomycosis. Aspergillus spp. was the most frequently isolated etiologic agent of onychomycosis due to NDM (83.0%). Other causative agents were Scopulariopsis brevicaulis (10.2%), Acremonium spp. (3.4%), Fusarium solani (1.7%), and Chaetomium globosum (1.7%). Conclusion Because of the increase in onychomycosis due to NDM, we suggest the need of a careful mycological examination in patients with onychomycosis. PMID:22577268

  16. Attenuation correction in SPECT images using attenuation map estimation with its emission data

    NASA Astrophysics Data System (ADS)

    Tavakoli, Meysam; Naji, Maryam; Abdollahi, Ali; Kalantari, Faraz

    2017-03-01

    Photon attenuation during SPECT imaging significantly degrades the diagnostic outcome and the quantitative accuracy of final reconstructed images. It is well known that attenuation correction can be done by using iterative reconstruction methods if we access to attenuation map. Two methods have been used to calculate the attenuation map: transmission-based and transmissionless techniques. In this phantom study, we evaluated the importance of attenuation correction by quantitative evaluation of errors associated with each method. For transmissionless approach, the attenuation map was estimated from the emission data only. An EM algorithm with attenuation model was developed and used for attenuation correction during image reconstruction. Finally, a comparison was done between reconstructed images using our OSEM code and analytical FBP method before and after attenuation correction. The results of measurements showed that: our programs are capable to reconstruct SPECT images and correct the attenuation effects. Moreover, to evaluate reconstructed image quality before and after attenuation correction we applied a novel approach using Image Quality Index. Attenuation correction increases the quality and quantitative accuracy in both methods. This increase is independent of activity in quantity factor and decreases with activity in quality factor. In EM algorithm, it is necessary to use regularization to obtain true distribution of attenuation coefficients.

  17. C-band attenuation by tropical rainfall in Darwin, Australia, using climatologically tuned Z(e)-R relations

    NASA Technical Reports Server (NTRS)

    Atlas, David; Rosenfeld, Daniel; Wolff, David B.

    1993-01-01

    The probability matching method (PMM) is used as a basis for estimating attenuation in tropical rains near Darwin, Australia. PMM provides a climatological relationship between measured radar reflectivity and rain rate, which includes the effects of rain and cloud attenuation. When the radar sample is representative, PMM estimates the rainfall without bias. When the data are stratified for greater than average rates, the method no longer compensates for the higher attenuation and the radar rainfall estimates are biased low. The uncompensated attenuation is used to estimate the climatological attenuation coefficient. The two-way attenuation coefficient was found to be 0.0085 dB/km ( mm/h) exp -1.08 for the tropical rains and associated clouds in Darwin for the first two months of the year for horizontally polarized radiation at 5.63 GHz. This unusually large value is discussed. The risks of making real-time corrections for attenuation are also treated.

  18. C-band attenuation by tropical rainfall in Darwin, Australia, using climatologically tuned Z(e)-R relations

    NASA Technical Reports Server (NTRS)

    Atlas, David; Rosenfeld, Daniel; Wolff, David B.

    1993-01-01

    The probability matching method (PMM) is used as a basis for estimating attenuation in tropical rains near Darwin, Australia. PMM provides a climatological relationship between measured radar reflectivity and rain rate, which includes the effects of rain and cloud attenuation. When the radar sample is representative, PMM estimates the rainfall without bias. When the data are stratified for greater than average rates, the method no longer compensates for the higher attenuation and the radar rainfall estimates are biased low. The uncompensated attenuation is used to estimate the climatological attenuation coefficient. The two-way attenuation coefficient was found to be 0.0085 dB/km ( mm/h) exp -1.08 for the tropical rains and associated clouds in Darwin for the first two months of the year for horizontally polarized radiation at 5.63 GHz. This unusually large value is discussed. The risks of making real-time corrections for attenuation are also treated.

  19. Optimal ultrasonic array focusing in attenuative media.

    PubMed

    Ganguli, A; Gao, R X; Liang, K; Jundt, J

    2011-12-01

    This paper presents a parametric study on the efficiency of ultrasound focusing in an attenuative medium, using phased arrays. Specifically, an analytical model of ultrasound wave focusing in a homogeneous, isotropic and attenuative fluid with point sources is presented. Calculations based on the model have shown that in an attenuative medium, an optimum frequency exists for the best focusing performance for a particular size of aperture and focal distance. The effect of different f numbers on the focusing performance in the attenuative medium is further investigated. The information obtained from the analytical model provides insights into the design and installation of a phased transducer array for energy efficient wave focusing.

  20. 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.

  1. MLAA-based attenuation correction of flexible hardware components in hybrid PET/MR imaging.

    PubMed

    Heußer, Thorsten; Rank, Christopher M; Berker, Yannick; Freitag, Martin T; Kachelrieß, Marc

    2017-12-01

    Accurate PET quantification demands attenuation correction (AC) for both patient and hardware attenuation of the 511 keV annihilation photons. In hybrid PET/MR imaging, AC for stationary hardware components such as patient table and MR head coil is straightforward, employing CT-derived attenuation templates. AC for flexible hardware components such as MR-safe headphones and MR radiofrequency (RF) surface coils is more challenging. Registration-based approaches, aligning CT-based attenuation templates with the current patient position, have been proposed but are not used in clinical routine. Ignoring headphone or RF coil attenuation has been shown to result in regional activity underestimation values of up to 18%. We propose to employ the maximum-likelihood reconstruction of attenuation and activity (MLAA) algorithm to estimate the attenuation of flexible hardware components. Starting with an initial attenuation map not including flexible hardware components, the attenuation update of MLAA is applied outside the body outline only, allowing to estimate hardware attenuation without modifying the patient attenuation map. Appropriate prior expectations on the attenuation coefficients are incorporated into MLAA. The proposed method is investigated for non-TOF PET phantom and (18)F-FDG patient data acquired with a clinical PET/MR device, using headphones or RF surface coils as flexible hardware components. Although MLAA cannot recover the exact physical shape of the hardware attenuation maps, the overall attenuation of the hardware components is accurately estimated. Therefore, the proposed algorithm significantly improves PET quantification. Using the phantom data, local activity underestimation when neglecting hardware attenuation was reduced from up to 25% to less than 3% under- or overestimation as compared to reference scans without hardware present or to CT-derived AC. For the patient data, we found an average activity underestimation of 7.9% evaluated in the full

  2. Differential evolution based prediction of rain attenuation over a LOS terrestrial link situated in the southern United Kingdom

    NASA Astrophysics Data System (ADS)

    Develi, Ibrahim

    2007-06-01

    The principal objective of a rain attenuation prediction method is to achieve acceptable estimates of the attenuation incurred on the signal due to rain. In this paper, a differential evolution (DE) based model for predicting rain attenuation in a terrestrial point-to-point line of sight (LOS) link at 97 GHz is proposed using previously available experimental data obtained in the southern United Kingdom. Rainfall rate and percentage of time are used as input data in the proposed prediction model. Excellent agreement between the experimental data and the model output indicates that the presented DE based method may efficiently be used for accurate prediction of the rain attenuation levels.

  3. Investigating the synergistic impedance match and attenuation effect of Co@C composite through adjusting the permittivity and permeability

    NASA Astrophysics Data System (ADS)

    Li, Daoran; Liang, Xiaohui; Quan, Bin; Cheng, Yan; Ji, Guangbin; Du, Youwei

    2017-03-01

    Impedance matching and microwave attenuation play key roles in electromagnetic absorption. Moderate electromagnetic parameters will lead to matched impedance matching and attenuation ability. Using magnetic/dielectric composites is considered to be an efficient strategy for achieving excellent electromagnetic absorbing properties. The Co@C reported in this research not only resulted in improved impedance matching behavior, but also possessed strong microwave attenuation ability due to its polarizing and conducting features. As a result, the effective absorption frequency of the optimal absorber covers 4.2 GHz under a thin coating layer of 1.4 mm. The attenuation mechanism has also been discussed in depth in this study.

  4. 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

  5. Influence of modal attenuation on shallow water propagation

    NASA Astrophysics Data System (ADS)

    Saintval, Wendy

    2008-12-01

    A recent simplification of Biot theory is used to illustrate relationships between the intrinsic sediment attenuation, the attenuation of individual modes (as expressed by the modal attenuation coefficients or MACs), and the energy loss of the total field. The simplest two-layer, isospeed waveguides yield MACs that decrease from f-2 to f-1 as frequency f becomes large. A heuristic modification of the environment suggests how a change in the magnitude and frequency behavior of the MACs may arise. We demonstrate how the MACs increase with the incorporation of a fluid-saturated porous layer in the waveguide by using a convenient parameterization and numerical results. The frequency power-law behavior observed increases from f0.7 to f1.7 as the thickness of this layer increases from 2% to 15% of the water depth. Numerical calculations for more realistic waveguides use sandy bottom sediments and isospeed, linear, and piecewise linear water depth profiles. These are environmental simplifications that preserve key features of waveguides from experiments near the New Jersey continental shelf. Principal characteristics of the calculated MACs at frequencies up to 2 kHz include: increased magnitude in the presence of near-interface gradients, reordering of least-attenuated modes for downward refracting water sound speed profiles, and variations of frequency behavior from f-1 to f1. We also demonstrate the sensitivity of the MACs to experimentally-determined upward, isospeed, and downward-refracting sound speed profiles in a shallow water environment with sandy, depositional layers located in the Gulf of Mexico. A comparison of these results with previous numerical studies shows good agreement with water sound speed profiles for nearly isospeed and weakly downward refracting cases. Water sound speed has a significant influence on modal attenuation and, consequently, on the effective attenuation coefficient, which estimates the average transmission decrease with range. The

  6. Live attenuated vaccines against pertussis.

    PubMed

    Locht, Camille; Mielcarek, Nathalie

    2014-09-01

    The intensive use of pertussis vaccines has dramatically reduced the incidence of whooping cough during the 20th century. However, recent outbreaks in countries with high vaccination coverage illustrate the shortcomings of current vaccination regimens, and immunity induced by the most recent, acellular vaccines wanes much faster than anticipated. As an alternative, live attenuated vaccine candidates have recently been developed in order to mimic natural infection, which induces long-lasting immunity. One of them has successfully completed a Phase I trial in humans and is now undergoing further product and clinical developments. This article describes the development of such vaccines, discusses their advantages over existing vaccines and their interesting bystander properties as powerful anti-inflammatory agents, which widens their potential use far beyond that for protection against whooping cough.

  7. Focal dural arteriovenous fistula (DAVF) presenting with progressive cognitive impairment including amnesia and alexia.

    PubMed

    Hasumi, Takashi; Fukushima, Takeshi; Haisa, Toshihiko; Yonemitsu, Tsutomu; Waragai, Masaaki

    2007-01-01

    A 75-year-old woman with a dural arteriovenous fistula (DAVF) presented with progressive cognitive impairment including amnesia and alexia. Neuroradiological studies showed a relatively confined DAVF lesion in the left temporal lobe. The patient did not have a history of trauma and did not complain of headache or tinnitus. Amnesia and alexia dramatically improved upon treatment of the DAVF, and this was associated with attenuation of an abnormal MRI signal in the left temporal lobe. The results suggest that gradually impaired cerebral circulation due to focal venous hypertensive encephalopathy localized to the left temporal lobe and resulting from a DAVF could be involved in slowly progressive amnesia and alexia. The case also shows that an intracranial DAVF may present as a variety of neurological symptoms, depending on its localization, size and clinical stage.

  8. 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

    2013-06-07

    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.

  9. 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.

  10. High Attenuation Rate for Shallow, Small Earthquakes in Japan

    NASA Astrophysics Data System (ADS)

    Si, Hongjun; Koketsu, Kazuki; Miyake, Hiroe

    2017-03-01

    We compared the attenuation characteristics of peak ground accelerations (PGAs) and velocities (PGVs) of strong motion from shallow, small earthquakes that occurred in Japan with those predicted by the equations of Si and Midorikawa (J Struct Constr Eng 523:63-70, 1999). The observed PGAs and PGVs at stations far from the seismic source decayed more rapidly than the predicted ones. The same tendencies have been reported for deep, moderate, and large earthquakes, but not for shallow, moderate, and large earthquakes. This indicates that the peak values of ground motion from shallow, small earthquakes attenuate more steeply than those from shallow, moderate or large earthquakes. To investigate the reason for this difference, we numerically simulated strong ground motion for point sources of M w 4 and 6 earthquakes using a 2D finite difference method. The analyses of the synthetic waveforms suggested that the above differences are caused by surface waves, which are predominant at stations far from the seismic source for shallow, moderate earthquakes but not for shallow, small earthquakes. Thus, although loss due to reflection at the boundaries of the discontinuous Earth structure occurs in all shallow earthquakes, the apparent attenuation rate for a moderate or large earthquake is essentially the same as that of body waves propagating in a homogeneous medium due to the dominance of surface waves.

  11. 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

  12. 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

  13. Extract from Mimosa pigra attenuates chronic experimental pulmonary hypertension.

    PubMed

    Rakotomalala, G; Agard, C; Tonnerre, P; Tesse, A; Derbré, S; Michalet, S; Hamzaoui, J; Rio, M; Cario-Toumaniantz, C; Richomme, P; Charreau, B; Loirand, G; Pacaud, P

    2013-06-21

    Different parts of Mimosa pigra (MPG) are used in traditional medicine in Madagascar, tropical Africa, South America and Indonesia for various troubles including cardiovascular disorders. To investigate the mechanisms underlying the vascular effects of MPG by assessing in vitro its antioxidant and anti-inflammatory properties, and its vascular relaxing effects, and in vivo, its action on hypoxic pulmonary hypertension (PAH) in rats. The antioxidant activity of MPG leaf hydromethanolic extract was determined by using both the 1,1-diphenyl-2-picrylhydrazyl radical scavenging and the oxygen radical absorbance capacity in vitro assays. Anti-inflammatory properties were assayed on TNFα-induced VCAM-1 expression in endothelial cells. The vasorelaxant effect of MPG extract was studied on rat arterial rings pre-contracted with phenylephrine (1μM) in the presence or absence of the endothelium. In vivo MPG extract effects were analyzed in chronic hypoxic PAH, obtained by housing male Wistar rats, orally treated or not with MPG extract (400mg/kg/d), in a hypobaric chamber for 21 days. MPG leaf extract had antioxidant and anti-inflammatory properties. It induced endothelium-dependent, NO-mediated relaxation of rat aorta and pulmonary artery. In vivo, chronic MPG treatment reduced hypoxic PAH in rat by decreasing by 22.3% the pulmonary arterial pressure and by 20.0% and 23.9% the pulmonary artery and cardiac remodelling, respectively. This effect was associated with a restoration of endothelium function and a 2.3-fold increase in endothelial NO synthase phosphorylation. MPG leaf hydromethanolic extract contained tryptophan and flavonoids, including quercetin glycosides. Both compounds also efficiently limit hypoxia-induced PAH. Our results show endothelial protective action of MPG leaf hydromethanolic extract which is likely to be due to its antioxidant action. MPG successfully attenuated the development of PAH, thus demonstrating the protective effect of MPG on

  14. Human due diligence.

    PubMed

    Harding, David; Rouse, Ted

    2007-04-01

    Most companies do a thorough job of financial due diligence when they acquire other companies. But all too often, deal makers simply ignore or underestimate the significance of people issues in mergers and acquisitions. The consequences are severe. Most obviously, there's a high degree of talent loss after a deal's announcement. To make matters worse, differences in decision-making styles lead to infighting; integration stalls; and productivity declines. The good news is that human due diligence can help companies avoid these problems. Done early enough, it helps acquirers decide whether to embrace or kill a deal and determine the price they are willing to pay. It also lays the groundwork for smooth integration. When acquirers have done their homework, they can uncover capability gaps, points of friction, and differences in decision making. Even more important, they can make the critical "people" decisions-who stays, who goes, who runs the combined business, what to do with the rank and file-at the time the deal is announced or shortly thereafter. Making such decisions within the first 30 days is critical to the success of a deal. Hostile situations clearly make things more difficult, but companies can and must still do a certain amount of human due diligence to reduce the inevitable fallout from the acquisition process and smooth the integration. This article details the steps involved in conducting human due diligence. The approach is structured around answering five basic questions: Who is the cultural acquirer? What kind of organization do you want? Will the two cultures mesh? Who are the people you most want to retain? And how will rank-and-file employees react to the deal? Unless an acquiring company has answered these questions to its satisfaction, the acquisition it is making will be very likely to end badly.

  15. Attenuation estimation using the peak frequency method with high-resolution time-frequency transforms

    NASA Astrophysics Data System (ADS)

    Tary, J. B.; Van der Baan, M.; Herrera, R. H.

    2016-12-01

    Seismic waves attenuate during their propagation due to Earth anelasticity. Attenuation is usually estimated by frequency domain methods such as the spectral ratio and frequency shift methods. These methods compare large frequency bandwidths of the spectra of two waveforms to compute attenuation. Time-frequency distribution resulting from high-resolution time-frequency transforms are highly localized which prevent their use to compute attenuation with these methods.The peak frequency method only requires the estimation of peak frequencies for a pair of waveforms to estimate attenuation, which is then compatible with high-resolution transforms. We here employ three transforms, namely basis pursuit, synchrosqueezing transform, and complete ensemble empirical mode decomposition (CEEMD). We evaluate their performance regarding attenuation estimation using synthetic examples with different signal-to-noise ratios, and compare their results to those of the spectral ratio and frequency shift methods. In most cases basis pursuit and the synchrosqueezing transform provide accurate results, while CEEMD show a higher sensitivity to the presence of noise.We then apply the three high-resolution transforms and the peak frequency method to two case studies, a seismic reflection profile and a vertical seismic profile (VSP). We employ centroid frequencies instead of peak frequencies because they provide stabler frequency estimates which are then transferred to stabler attenuation estimates. In the case of the seismic reflection profile, the three time-frequency transforms show small increases in centroid frequencies superimposed on a general decreasing trend. This likely corresponds to local tuning effects due to the layering superimposed on the effect of intrinsic attenuation. For the VSP, the three time-frequency transforms show consistent patterns in centroid frequencies and quality factors. These results show the worth of high-resolution transforms for attenuation estimation.

  16. Maternal mortality due to violence.

    PubMed

    Rizzi, R G; Córdoba, R R; Maguna, J J

    1998-12-01

    The objectives were to investigate the death of women by violent injuries, including induced abortion, in the Province of Córdoba, Argentina, 1992-1996 and to perform a bibliographic review on maternal death due to violence. Reports of autopsies of all violent deaths in women aged 12-44 years were reviewed to determine the cause of death for cases of suicide, homicide, accident or induced abortion and a bibliographic review was performed through MEDLINE. Two hundred and seventy two women died due to violence, including 22 which were due to complications of induced abortion. The remaining 250 deaths were: 44 (17.6%) by suicide, 51 (20.4%) by homicide and 155 (62%) by traffic accidents, including 6 pregnant women (2 died by suicide, 1 by homicide and 3 by accidents). Violence against women and pregnant women is a growing problem in developing countries. The implication of a simplified screening has been proposed to identify abuses against women, searching for frequency of abuse, its severity and to determine who provokes it.

  17. Markless Attenuation Correction for Carotid MRI Surface Receiver Coils in Combined PET/MR Imaging

    PubMed Central

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

    2015-01-01

    Purpose To evaluate the effect of attenuation of MR coils on quantitative carotid PET/MR exams. Additionally, to develop and evaluate automated attenuation correction method for flexible carotid MR coils was developed and evaluated. Methods 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 minutes 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. Results 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. Conclusions 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

  18. 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.

  19. Efficacy and effectiveness of live attenuated influenza vaccine in school-age children.

    PubMed

    Coelingh, Kathleen; Olajide, Ifedapo Rosemary; MacDonald, Peter; Yogev, Ram

    2015-01-01

    Evidence of high efficacy of live attenuated influenza vaccine (LAIV) from randomized controlled trials is strong for children 2-6 years of age, but fewer data exist for older school-age children. We reviewed the published data on efficacy and effectiveness of LAIV in children ≥5 years. QUOSA (Elsevier database) was searched for articles published from January 1990 to June 2014 that included 'FluMist', 'LAIV', 'CAIV', 'cold adapted influenza vaccine', 'live attenuated influenza vaccine', 'live attenuated cold adapted' or 'flu mist'. Studies evaluated included randomized controlled trials, effectiveness and indirect protection studies. This review demonstrates that LAIV has considerable efficacy and effectiveness in school-age children.

  20. Endurance training attenuates the increase in peripheral chemoreflex sensitivity with intermittent hypoxia.

    PubMed

    Miller, Amanda J; Sauder, Charity L; Cauffman, Aimee E; Blaha, Cheryl A; Leuenberger, Urs A

    2017-02-01

    Patients with heart failure and sleep apnea have greater chemoreflex sensitivity, presumably due to intermittent hypoxia (IH), and this is predictive of mortality. We hypothesized that endurance training would attenuate the effect of IH on peripheral chemoreflex sensitivity in healthy humans. Fifteen young healthy subjects (9 female, 26 ± 1 yr) participated. Between visits, 11 subjects underwent 8 wk of endurance training that included running four times/wk at 80% predicted maximum heart rate and interval training, and four control subjects did not change activity. Chemoreflex sensitivity (the slope of ventilation responses to serial oxygen desaturations), blood pressure, heart rate, and muscle sympathetic nerve activity (MSNA) were assessed before and after 30 min of IH. Endurance training decreased resting systolic blood pressure (119 ± 3 to 113 ± 3 mmHg; P = 0.027) and heart rate (67 ± 3 to 61 ± 2 beats/min; P = 0.004) but did not alter respiratory parameters at rest (P > 0.2). Endurance training attenuated the IH-induced increase in chemoreflex sensitivity (pretraining: Δ 0.045 ± 0.026 vs. posttraining: Δ -0.028 ± 0.040 l·min(-1)·% O2 desaturation(-1); P = 0.045). Furthermore, IH increased mean blood pressure and MSNA burst rate before training (P < 0.05), but IH did not alter these measures after training (P > 0.2). All measurements were similar in the control subjects at both visits (P > 0.05). Endurance training attenuates chemoreflex sensitization to IH, which may partially explain the beneficial effects of exercise training in patients with cardiovascular disease. Copyright © 2017 the American Physiological Society.

  1. GABAB receptor activation attenuates the stimulant but not mesolimbic dopamine response to ethanol in FAST mice

    PubMed Central

    Holstein, Sarah E.; Li, Na; Eshleman, Amy J.; Phillips, Tamara J.

    2012-01-01

    Neural processes influenced by γ-aminobutyric acid B (GABAB) receptors appear to contribute to acute ethanol sensitivity, including the difference between lines of mice bred for extreme sensitivity (FAST) or insensitivity (SLOW) to the locomotor stimulant effect of ethanol. One goal of the current study was to determine whether selection of the FAST and SLOW lines resulted in changes in GABAB receptor function, since the lines differ in sensitivity to the GABAB receptor agonist baclofen and baclofen attenuates the stimulant response to ethanol in FAST mice. A second goal was to determine whether the baclofen-induced reduction in ethanol stimulation in FAST mice is associated with an attenuation of the mesolimbic dopamine response to ethanol. In Experiment 1, the FAST and SLOW lines were found to not differ in GABAB receptor function (measured by baclofen-stimulated [35S]GTP!S binding) in whole brain or in several regional preparations, except in the striatum in one of the two replicate sets of selected lines. In Experiment 2, baclofen-induced attenuation of the locomotor stimulant response to ethanol in FAST mice was not accompanied by a reduction in dopamine levels in the nucleus accumbens, as measured by microdialysis. These data suggest that, overall, GABAB receptor function does not play an integral role in the genetic difference in ethanol sensitivity between the FAST and SLOW lines. Further, although GABAB receptors do modulate the locomotor stimulant response to ethanol in FAST mice, this effect does not appear to be due to a reduction in tonic dopamine signaling in the nucleus accumbens. PMID:22982185

  2. Serelaxin Treatment Reduces Oxidative Stress and Increases Aldehyde Dehydrogenase-2 to Attenuate Nitrate Tolerance

    PubMed Central

    Leo, Chen Huei; Fernando, Dhanushke T.; Tran, Lillie; Ng, Hooi Hooi; Marshall, Sarah A.; Parry, Laura J.

    2017-01-01

    Background: Glyceryl trinitrate (GTN) is a commonly prescribed treatment for acute heart failure patients. However, prolonged GTN treatment induces tolerance, largely due to increased oxidative stress and reduced aldehyde dehydrogenase-2 (ALDH-2) expression. Serelaxin has several vasoprotective properties, which include reducing oxidative stress and augmenting endothelial function. We therefore tested the hypothesis in rodents that serelaxin treatment could attenuate low-dose GTN-induced tolerance. Methods and Results: Co-incubation of mouse aortic rings ex vivo with GTN (10 μM) and serelaxin (10 nM) for 1 h, restored GTN responses, suggesting that serelaxin prevented the development of GTN tolerance. Male Wistar rats were subcutaneously infused with ethanol (control), low-dose GTN+placebo or low-dose GTN+serelaxin via osmotic minipumps for 3 days. Aortic vascular function and superoxide levels were assessed using wire myography and lucigenin-enhanced chemiluminescence assay respectively. Changes in aortic ALDH-2 expression were measured by qPCR and Western blot respectively. GTN+placebo infusion significantly increased superoxide levels, decreased ALDH-2 and attenuated GTN-mediated vascular relaxation. Serelaxin co-treatment with GTN significantly enhanced GTN-mediated vascular relaxation, reduced superoxide levels and increased ALDH-2 expression compared to GTN+placebo-treated rats. Conclusion: Our data demonstrate that a combination of serelaxin treatment with low dose GTN attenuates the development of GTN-induced tolerance by reducing superoxide production and increasing ALDH-2 expression in the rat aorta. We suggest that serelaxin may improve nitrate efficacy in a clinical setting. PMID:28377719

  3. Attenuation of 7 GHz surface acoustic waves on silicon

    NASA Astrophysics Data System (ADS)

    Li, Dongyao; Cahill, David G.

    2016-09-01

    We measured the attenuation of GHz frequency surface acoustic waves (SAWs) on the Si (001) surface using an optical pump-probe technique at temperatures between 300 and 600 K. SAWs are generated and detected by a 700 nm Al grating fabricated by nanoimprint lithography. The grating for SAW generation is separated from the grating for SAW detection by ≈150 μ m . The amplitude of SAWs is attenuated by coupling to bulk waves created by the Al grating, diffraction due to the finite size of the source, and the intrinsic relaxational Akhiezer damping of elastic waves in Si. Thermal phonon relaxation time and Grüneisen parameters are fitted using temperature-dependent measurement. The f Q product of a hypothetical micromechanical oscillator limited by Akhiezer damping at this frequency is ˜3 ×1013 Hz.

  4. 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

  5. Apparent seismic attenuation observations in Australia

    NASA Astrophysics Data System (ADS)

    Smale, J.; Bezada, M.

    2016-12-01

    Seismic attenuation is a valuable observation that can provide insight into lithospheric structure complementary to the more commonly studied seismic velocity. We map apparent attenuation beneath the Australian mainland and Tasmania using 21 deep-focus teleseismic events recorded on Geoscience Australia's seismic network. In contrast to the traditional frequency-domain approach, we use a time-domain based procedure. For each event, we estimate a source waveform from the highest quality recordings, apply an attenuation operator to the source estimate using a range of t* values to find the best fit to the record at each station, and invert the ensemble of t* estimates to produce a smooth map. Our results are broadly consistent with velocity models obtained from surface-wave tomography. Lowest apparent attenuation occurs in the Northern Territory near Darwin, with low attenuation appearing to extend down to the Southern Territory's southern coast. The Archean Gawler, Pilbara and Yilgarn cratons also correspond to regions of lower attenuation. New South Wales and Victoria are primarily dominated by high attenuation values, with the highest apparent attenuation occurring in Tasmania, possibly associated with the East Australia Plume System.

  6. LONG TERM MONITORING FOR NATURAL ATTENUATION

    EPA Science Inventory

    We have good statistical methods to: (1) determine whether concentrations of a contaminant are attenuating over time, (2) determine the rate of attenuation and confidence interval on the rate, and (3) determine whether concentrations have met a particular clean up goal. We do no...

  7. LONG TERM MONITORING FOR NATURAL ATTENUATION

    EPA Science Inventory

    We have good statistical methods to: (1) determine whether concentrations of a contaminant are attenuating over time, (2) determine the rate of attenuation and confidence interval on the rate, and (3) determine whether concentrations have met a particular clean up goal. We do no...

  8. 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.

  9. Dehydroepiandrosterone Attenuates Cocaine-Seeking Behaviour Independently of Corticosterone Fluctuations.

    PubMed

    Maayan, R; Hirsh, L; Yadid, G; Weizman, A

    2015-11-01

    The neurosteroid dehydroepiandrosterone (DHEA) is involved in the pathophysiology of several psychiatric disorders, including cocaine addiction. We have previously shown that DHEA attenuates cocaine-seeking behaviour, and also that DHEA decreases corticosterone (CORT) levels in plasma and the prefrontal cortex. Previous studies have found that rats demonstrate cocaine-seeking behaviour only when the level of CORT reaches a minimum threshold. In the present study, we investigated whether the attenuating effect of DHEA on cocaine seeking is a result of it reducing CORT levels rather than a result of any unique neurosteroid properties. Rats received either daily DHEA injections (2 mg/kg, i.p.) alone, daily DHEA (2 mg/kg, i.p.) with CORT infusion (to maintain stable basal levels of CORT; 15 mg/kg, s.c.) or vehicle (i.p.) as control, throughout self-administration training and extinction sessions. We found that both DHEA-treated and DHEA + CORT-treated groups showed a significantly lower number of active lever presses compared to controls throughout training and extinction sessions, as well as at cocaine-primed reinstatement. DHEA-treated rats showed lower CORT levels throughout the experimental phases compared to DHEA + CORT-treated and control rats. Additionally, we show that DHEA administered to cocaine-trained rats throughout extinction sessions, or immediately before reinstatement, attenuated cocaine seeking. These findings indicate that DHEA attenuates cocaine-seeking behaviour independently of fluctuations in CORT levels.

  10. Urgent challenges in implementing live attenuated influenza vaccine.

    PubMed

    Singanayagam, Anika; Zambon, Maria; Lalvani, Ajit; Barclay, Wendy

    2017-08-02

    Conflicting reports have emerged about the effectiveness of the live attenuated influenza vaccine. The live attenuated influenza vaccine appears to protect particularly poorly against currently circulating H1N1 viruses that are derived from the 2009 pandemic H1N1 viruses. During the 2015-16 influenza season, when pandemic H1N1 was the predominant virus, studies from the USA reported a complete lack of effectiveness of the live vaccine in children. This finding led to a crucial decision in the USA to recommend that the live vaccine not be used in 2016-17 and to switch to the inactivated influenza vaccine. Other countries, including the UK, Canada, and Finland, however, have continued to recommend the use of the live vaccine. This policy divergence and uncertainty has far reaching implications for the entire global community, given the importance of the production capabilities of the live attenuated influenza vaccine for pandemic preparedness. In this Personal View, we discuss possible explanations for the observed reduced effectiveness of the live attenuated influenza vaccine and highlight the underpinning scientific questions. Further research to understand the reasons for these observations is essential to enable informed public health policy and commercial decisions about vaccine production and development in coming years. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Wogonin Induces Eosinophil Apoptosis and Attenuates Allergic Airway Inflammation

    PubMed Central

    Dorward, David A.; Sharma, Sidharth; Rennie, Jillian; Felton, Jennifer M.; Alessandri, Ana L.; Duffin, Rodger; Schwarze, Jurgen; Haslett, Christopher; Rossi, Adriano G.

    2015-01-01

    Rationale: Eosinophils are key effector cells in allergic diseases, including allergic rhinitis, eczema, and asthma. Their tissue presence is regulated by both recruitment and increased longevity at inflamed sites. Objectives: To investigate the ability of the flavone wogonin to induce eosinophil apoptosis in vitro and attenuate eosinophil-dominant allergic inflammation in vivo in mice. Methods: Human and mouse eosinophil apoptosis in response to wogonin was investigated by cellular morphology, flow cytometry, mitochondrial membrane permeability, and pharmacological caspase inhibition. Allergic lung inflammation was modeled in mice sensitized and challenged with ovalbumin. Bronchoalveolar lavage (BAL) and lung tissue were examined for inflammation, mucus production, and inflammatory mediator production. Airway hyperresponsiveness to aerosolized methacholine was measured. Measurements and Main Results: Wogonin induced time- and concentration-dependent human and mouse eosinophil apoptosis in vitro. Wogonin-induced eosinophil apoptosis occurred with activation of caspase-3 and was inhibited by pharmacological caspase inhibition. Wogonin administration attenuated allergic airway inflammation in vivo with reductions in BAL and interstitial eosinophil numbers, increased eosinophil apoptosis, reduced airway mucus production, and attenuated airway hyperresponsiveness. This wogonin-induced reduction in allergic airway inflammation was prevented by concurrent caspase inhibition in vivo. Conclusions: Wogonin induces eosinophil apoptosis and attenuates allergic airway inflammation, suggesting that it has therapeutic potential for the treatment of allergic inflammation in humans. PMID:25629436

  12. Preerythrocytic, live-attenuated Plasmodium falciparum vaccine candidates by design.

    PubMed

    VanBuskirk, Kelley M; O'Neill, Matthew T; De La Vega, Patricia; Maier, Alexander G; Krzych, Urszula; Williams, Jack; Dowler, Megan G; Sacci, John B; Kangwanrangsan, Niwat; Tsuboi, Takafumi; Kneteman, Norman M; Heppner, Donald G; Murdock, Brant A; Mikolajczak, Sebastian A; Aly, Ahmed S I; Cowman, Alan F; Kappe, Stefan H I

    2009-08-04

    Falciparum malaria is initiated when Anopheles mosquitoes transmit the Plasmodium sporozoite stage during a blood meal. Irradiated sporozoites confer sterile protection against subsequent malaria infection in animal models and humans. This level of protection is unmatched by current recombinant malaria vaccines. However, the live-attenuated vaccine approach faces formidable obstacles, including development of accurate, reproducible attenuation techniques. We tested whether Plasmodium falciparum could be attenuated at the early liver stage by genetic engineering. The P. falciparum genetically attenuated parasites (GAPs) harbor individual deletions or simultaneous deletions of the sporozoite-expressed genes P52 and P36. Gene deletions were done by double-cross-over recombination to avoid genetic reversion of the knockout parasites. The gene deletions did not affect parasite replication throughout the erythrocytic cycle, gametocyte production, mosquito infections, and sporozoite production rates. However, the deletions caused parasite developmental arrest during hepatocyte infection. The double-gene deletion line exhibited a more severe intrahepatocytic growth defect compared with the single-gene deletion lines, and it did not persist. This defect was assessed in an in vitro liver-stage growth assay and in a chimeric mouse model harboring human hepatocytes. The strong phenotype of the double knockout GAP justifies its human testing as a whole-organism vaccine candidate using the established sporozoite challenge model. GAPs might provide a safe and reproducible platform to develop an efficacious whole-cell malaria vaccine that prevents infection at the preerythrocytic stage.

  13. Radiation attenuation and opacity in smoke and water sprays

    NASA Astrophysics Data System (ADS)

    Parent, Gilles; Boulet, Pascal; Morlon, Romain; Blanchard, Elizabeth

    2017-08-01

    Radiation attenuation through sprays, smoke and mixings of both media was studied in the infrared and in the visible range, by conducting real scale experiments in a corridor. The effect of water injection by a water mist nozzle and a sprinkler device was investigated. Radiation attenuation in the infrared range and opacity in the visible range were measured, by using a FTIR spectrometer and a dedicated opacimetry device especially designed for the present application. Experiments were done using either a blackbody source for attenuation characterization, or a heptane pool fire aimed at producing smoke for opacity measurements. For tests with smoke, the difficulties raised by the harsh environment involving a hot mixing of gas plus soot and vapor carrying water droplets were circumvented with an original device involving an optical fiber network. Mean infrared transmission was found equal to 12% for the water mist (with a 25 L/min water flowrate) and 37% for the sprinkler (with a 91 L/min water flowrate). Fitting the infrared transmission spectra with results obtained using a Monte Carlo simulation provided an estimation of the water volumetric fraction in the spray. It was shown that the better attenuation capability of the water mist is due to two factors: (1) a higher extinction coefficient of the water mist for a given water volumetric fraction due to the small size of the injected droplets and (2) a higher water volumetric fraction. Opacity measurements in the visible range yielded a measured extinction coefficient in good agreement with an estimation obtained with the Mie theory and the identified water volumetric fraction. Moreover, the water sprays (sprinkler or water mist) was seen to lead to a quick de-stratification of the smoke layer. When the spraying operation was stopped, the visibility re-increased in two main steps: a first step of fast increase and a second step of slow increase needing a few tens of seconds to get again a fully stratified smoke

  14. Ablation of Programmed −1 Ribosomal Frameshifting in Venezuelan Equine Encephalitis Virus Results in Attenuated Neuropathogenicity

    PubMed Central

    Kendra, Joseph A.; de la Fuente, Cynthia; Brahms, Ashwini; Woodson, Caitlin; Bell, Todd M.; Chen, Bin; Khan, Yousuf A.; Jacobs, Jonathan L.

    2016-01-01

    ABSTRACT The alphaviruses Venezuelan equine encephalitis virus (VEEV), eastern equine encephalitis virus (EEEV), and western equine encephalitis virus (WEEV) are arthropod-borne positive-strand RNA viruses that are capable of causing acute and fatal encephalitis in many mammals, including humans. VEEV was weaponized during the Cold War and is recognized as a select agent. Currently, there are no FDA-approved vaccines or therapeutics for these viruses. The spread of VEEV and other members of this family due to climate change-mediated vector range expansion underscores the need for research aimed at developing medical countermeasures. These viruses utilize programmed −1 ribosomal frameshifting (−1 PRF) to synthesize the viral trans-frame (TF) protein, which has previously been shown to be important for neuropathogenesis in the related Sindbis virus. Here, the alphavirus −1 PRF signals were characterized, revealing novel −1 PRF stimulatory structures. −1 PRF attenuation mildly affected the kinetics of VEEV accumulation in cultured cells but strongly inhibited its pathogenesis in an aerosol infection mouse model. Importantly, the decreased viral titers in the brains of mice infected with the mutant virus suggest that the alphavirus TF protein is important for passage through the blood-brain barrier and/or for neuroinvasiveness. These findings suggest a novel approach to the development of safe and effective live attenuated vaccines directed against VEEV and perhaps other closely related −1 PRF-utilizing viruses. IMPORTANCE Venezuelan equine encephalitis virus (VEEV) is a select agent that has been weaponized. This arthropod-borne positive-strand RNA virus causes acute and fatal encephalitis in many mammals, including humans. There is no vaccine or other approved therapeutic. VEEV and related alphaviruses utilize programmed −1 ribosomal frameshifting (−1 PRF) to synthesize the viral trans-frame (TF) protein, which is important for neuropathogenesis. −1

  15. Photoacoustic imaging taking into account thermodynamic attenuation

    NASA Astrophysics Data System (ADS)

    Acosta, Sebastián; Montalto, Carlos

    2016-11-01

    In this paper we consider a mathematical model for photoacoustic imaging which takes into account attenuation due to thermodynamic dissipation. The propagation of acoustic (compressional) waves is governed by a scalar wave equation coupled to the heat equation for the excess temperature. We seek to recover the initial acoustic profile from knowledge of acoustic measurements at the boundary. We recognize that this inverse problem is a special case of boundary observability for a thermoelastic system. This leads to the use of control/observability tools to prove the unique and stable recovery of the initial acoustic profile in the weak thermoelastic coupling regime. This approach is constructive, yielding a solvable equation for the unknown acoustic profile. Moreover, the solution to this reconstruction equation can be approximated numerically using the conjugate gradient method. If certain geometrical conditions for the wave speed are satisfied, this approach is well-suited for variable media and for measurements on a subset of the boundary. We also present a numerical implementation of the proposed reconstruction algorithm.

  16. HIGH-RESOLUTION SEISMIC VELOCITY AND ATTENUATION MODELS OF THE CAUCASUS-CASPIAN REGION

    SciTech Connect

    Mellors, R; Gok, R; Sandvol, E

    2007-07-10

    The southwest edge of Eurasia is a tectonically and structurally complex region that includes the Caspian and Black Sea basins, the Caucasus Mountains, and the high plateaus south of the Caucasus. Crustal and upper mantle velocities show great heterogeneity in this region and regional phases display variations in both amplitudes and travel time. Furthermore, due to a lack of quality data, the region has largely been unexplored in terms of the detailed lithospheric seismic structure. A unified high-resolution 3D velocity and attenuation model of the crust and upper mantle will be developed and calibrated. This model will use new data from 23 new broadband stations in the region analyzed with a comprehensive set of techniques. Velocity models of the crust and upper mantle will be developed using a joint inversion of receiver functions and surface waves. The surface wave modeling will use both event-based methods and ambient noise tomography. Regional phase (Pg, Pn, Sn, and Lg) Q model(s) will be constructed using the new data in combination with existing data sets. The results of the analysis (both attenuation and velocity modeling) will be validated using modeling of regional phases, calibration with selected events, and comparison with previous work. Preliminary analyses of receiver functions show considerable variability across the region. All results will be integrated into the KnowledgeBase.

  17. UV Attenuation Near Coral Reefs in the Florida Keys: Light Absorption by CDOM and Particles

    NASA Astrophysics Data System (ADS)

    Shank, G. C.; Zepp, R. G.; Bartels, E.

    2005-12-01

    We have investigated the roles of chromophoric dissolved organic matter (CDOM) and suspended particles in the attenuation of UV radiation in the middle and lower regions of the Florida Keys. Extended exposure to UV radiation, along with elevated sea surface temperatures, impairs physiological processes in corals and contributes to bleaching episodes. Corals in the Florida Keys experience large variations in UV exposure due to several factors including tidal exchange and fluctuating meteorological conditions. CDOM derived from mangroves and seagrass beds is the primary attenuator of UV radiation near coral reefs in our study area. CDOM accounts for more than 90 percent of the absorption of UVB irradiance (305 nm) throughout the region. However, we have determined using the quantitative filter technique that up to 25 percent of the downwelling UVA irradiance at 380 nm may be directly absorbed by suspended particles. Resuspension from within or near the reef structure appears to be the primary particle source as phytoplankton pigments typically comprise less than 20 percent of the particle UV absorption capacity near reef sampling sites. Our research also has implications for remote sensing applications as light absorbed by particles must be considered when modeling optical data from satellites. Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.

  18. Ablation of Programmed -1 Ribosomal Frameshifting in Venezuelan Equine Encephalitis Virus Results in Attenuated Neuropathogenicity.

    PubMed

    Kendra, Joseph A; de la Fuente, Cynthia; Brahms, Ashwini; Woodson, Caitlin; Bell, Todd M; Chen, Bin; Khan, Yousuf A; Jacobs, Jonathan L; Kehn-Hall, Kylene; Dinman, Jonathan D

    2017-02-01

    The alphaviruses Venezuelan equine encephalitis virus (VEEV), eastern equine encephalitis virus (EEEV), and western equine encephalitis virus (WEEV) are arthropod-borne positive-strand RNA viruses that are capable of causing acute and fatal encephalitis in many mammals, including humans. VEEV was weaponized during the Cold War and is recognized as a select agent. Currently, there are no FDA-approved vaccines or therapeutics for these viruses. The spread of VEEV and other members of this family due to climate change-mediated vector range expansion underscores the need for research aimed at developing medical countermeasures. These viruses utilize programmed -1 ribosomal frameshifting (-1 PRF) to synthesize the viral trans-frame (TF) protein, which has previously been shown to be important for neuropathogenesis in the related Sindbis virus. Here, the alphavirus -1 PRF signals were characterized, revealing novel -1 PRF stimulatory structures. -1 PRF attenuation mildly affected the kinetics of VEEV accumulation in cultured cells but strongly inhibited its pathogenesis in an aerosol infection mouse model. Importantly, the decreased viral titers in the brains of mice infected with the mutant virus suggest that the alphavirus TF protein is important for passage through the blood-brain barrier and/or for neuroinvasiveness. These findings suggest a novel approach to the development of safe and effective live attenuated vaccines directed against VEEV and perhaps other closely related -1 PRF-utilizing viruses.

  19. Practical aspects in the use of passive immunization as an alternative to attenuated viral vaccines.

    PubMed

    Aizenshtein, Elina; Yosipovich, Roni; Kvint, Moran; Shadmon, Roy; Krispel, Simcha; Shuster, Efrat; Eliyahu, Dalia; Finger, Avner; Banet-Noach, Caroline; Shahar, Ehud; Pitcovski, Jacob

    2016-05-11

    Passive immunization as a method to protect birds has been tested for many years and shown to be effective. Its advantages over active vaccination include no use of partially virulent viruses, overcoming the gap in the level of protection at young age due to interference of maternal antibodies to raise self-immune response following active vaccination and the possible immunosuppressive effect of attenuated vaccine viruses. However, a major obstacle to its implementation is its relatively high cost which is dependent, among other things, mainly on two factors: the efficacy of antibody production, and the use of specific pathogen-free (SPF) birds for antibody production to avoid the possible transfer of pathogens from commercial layers. In this study we show efficient production of immunoglobulin Y (IgY) against four different pathogens simultaneously in the same egg, and treatment of the extracted IgY with formalin to negate the need for SPF birds. Formalin, a common registered sterilization compound in vaccine production, was shown not to interfere with the Fab specific antigen binding or Fc-complement activation of the antibody. Following injection of 1-day-old broilers with antibodies against infectious bursal disease virus, protective antibody levels were acquired for the entire period of sensitivity to this pathogen (35 days). Passive vaccination with formalin-sterilized IgY against multiple antigens extracted from one commercial egg may be a cost-effective and advantageous complementary or alternative to attenuated vaccines in poultry. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Quantum dot-related genotoxicity perturbation can be attenuated by PEG encapsulation.

    PubMed

    Ju, Li; Zhang, Guanglin; Zhang, Chen; Sun, Li; Jiang, Ying; Yan, Chunlan; Duerksen-Hughes, Penelope J; Zhang, Xing; Zhu, Xinqiang; Chen, Fanqing Frank; Yang, Jun

    2013-04-30

    Nanomaterial-biosystem interaction is emerging as a major concern hindering wide adoption of nanomaterials. Using quantum dots (Qdots) of different sizes (Qdot-440nm and Qdot-680nm) as a model system, we studied the effects of polyethylene glycol (PEG) thin-layer surface modification in attenuating Qdot-related cytotoxicity, genotoxicity perturbation and oxidative stress in a cellular system. We found that uncoated Qdots (U-Qdots) made of core/shell CdSe/ZnS could indeed induce cytotoxic effects, including the inhibition of cell growth. Also, both the neutral comet assay and γH2AX foci formation showed that U-Qdots caused significant DNA damage in a time- and dose-dependent manner. In contrast, results from cytotoxicity analysis and γH2AX generation indicate minimal impact on cells after exposure to PEG-coated Qdots. This lack of observed toxic effects from PEG-coated Qdots may be due to the fact that PEG-coating can inhibit ROS generation induced by U-Qdots. Based on these observations, we conclude that the genotoxicity of Qdots could be significantly decreased following proper surface modification, such as PEG encapsulation. In addition, PEG encapsulation may also serve as a general method to attenuate nanotoxicity for other nanoparticles.

  1. [Onychomycoses due to molds].

    PubMed

    Chabasse, D; Pihet, M

    2014-12-01

    Onychomycoses represent about 30% of superficial mycosis that are encountered in Dermatology consults. Fungi such as dermatophytes, which are mainly found on the feet nails, cause nearly 50% of these onychopathies. Yeasts are predominantly present on hands, whereas non-dermatophytic moulds are very seldom involved in both foot and hand nails infections. According to literature, these moulds are responsible for 2 to 17% of onychomycoses. Nevertheless, we have to differentiate between onychomycoses due to pseudodermatophytes such as Neoscytalidium (ex-Scytalidium) and Onychocola canadensis, which present a high affinity for keratin, and onychomycoses due to filamentous fungi such as Aspergillus, Fusarium, Scopulariopsis, Acremonium... These saprophytic moulds are indeed most of the time considered as colonizers rather than real pathogens agents. Mycology and histopathology laboratories play an important role. They allow to identify the species that is involved in nail infection, but also to confirm parasitism by the fungus in the infected nails. Indeed, before attributing any pathogenic role to non-dermatophytic moulds, it is essential to precisely evaluate their pathogenicity through samples and accurate mycological and/or histological analysis. The treatment of onychomycoses due to non-dermatophytic moulds is difficult, as there is today no consensus. The choice of an antifungal agent will first depend on the species that is involved in the infection, but also on the severity of nail lesions and on the patient himself. In most cases, the onychomycosis will be cured with chemical or mechanical removing of the infected tissues, followed by a local antifungal treatment. In some cases, a systemic therapy will be discussed.

  2. Attenuation of an ultrasonic beam by suspended particles and range of acoustic flow meters in sewer networks.

    PubMed

    Larrarte, Frédérique; François, Pierre

    2012-01-01

    Ultrasonic flow meters are commonly used in wastewater management. Under certain circumstances, a reduction in the flow meter range may occur and cause significant error in the flow rate measurement. Attenuation due to suspended particles is one of the phenomena capable of reducing the flow meter range. The present paper examines attenuation resulting from re-suspended pond sediment over a wide range of concentration values. It appears that a formula established for sand suspensions provides a good estimate of ultrasound attenuation for these types of particles as well. Experiments conducted for wastewater under particle concentrations commonly encountered in sewer networks demonstrate that the attenuation by particles only contributes to a negligible extent towards intensity decay, in accordance with theoretical predictions. We also theoretically determine herein the operating conditions under which the range of an ultrasonic flow meter would be significantly reduced due to particle attenuation.

  3. Kelussia odoratissima Mozaff attenuates thromboembolic brain injury, possibly due to its Z-ligustilide content.

    PubMed

    Barzegar-Fallah, Niloofar; Baery, Nasrin; Soleymankhani, Majid; Malekmohammadi, Nafiseh; Alimoradi, Houman; Parsa, Abdolhamid; Barzegar-Fallah, Anita

    2016-01-01

    Essential oil (EO) of Kelussia odoratissima Mozaff, whose main composition is Z-ligustilide, has been shown to have strong antioxidant and anti-inflammatory effects and potent neuroprotective properties. This study examined whether or not the EO could ameliorate brain damage and behavioural dysfunction in a thromboembolic model of stroke in rats and compare its effects to that of the purified Z-ligustilide. Stroke was induced in rats by middle cerebral artery occlusion using an autologous pre-formed clot. EO (10 mg kg(-1) and 45 mg kg(-1)) and Z-ligustilide (20 mg kg(-1)) were injected intraperitoneally 1 h prior to embolization. Behavioural scores, infarct size and brain oedema, as well as the level of tumour necrosis factor-alpha (TNF-α), malondialdehyde, glutathione, catalase and superoxide dismutase activity were determined in the ipsilateral cortex 24 hours following stroke induction. EO (45 mg kg(-1)), statistically similar to Z-ligustilide (20 mg kg(-1)), curtailed brain infarction and oedema, improved behavioural scores and prevented enhanced oxidative stress and TNF-α level in the ischaemic brain tissues. The findings provide the first evidence of effectiveness of the extract in a thromboembolic model of stroke, whose action can be mediated, at least in part, by the antioxidative and anti-inflammatory mechanisms.

  4. Metabolic stress-induced cardiomyopathy is caused by mitochondrial dysfunction due to attenuated Erk5 signaling.

    PubMed

    Liu, Wei; Ruiz-Velasco, Andrea; Wang, Shoubao; Khan, Saba; Zi, Min; Jungmann, Andreas; Dolores Camacho-Muñoz, Maria; Guo, Jing; Du, Guanhua; Xie, Liping; Oceandy, Delvac; Nicolaou, Anna; Galli, Gina; Müller, Oliver J; Cartwright, Elizabeth J; Ji, Yong; Wang, Xin

    2017-09-08

    The prevalence of cardiomyopathy from metabolic stress has increased dramatically; however, its molecular mechanisms remain elusive. Here, we show that extracellular signal-regulated protein kinase 5 (Erk5) is lost in the hearts of obese/diabetic animal models and that cardiac-specific deletion of Erk5 in mice (Erk5-CKO) leads to dampened cardiac contractility and mitochondrial abnormalities with repressed fuel oxidation and oxidative damage upon high fat diet (HFD). Erk5 regulation of peroxisome proliferator-activated receptor γ co-activator-1α (Pgc-1α) is critical for cardiac mitochondrial functions. More specifically, we show that Gp91phox activation of calpain-1 degrades Erk5 in free fatty acid (FFA)-stressed cardiomyocytes, whereas the prevention of Erk5 loss by blocking Gp91phox or calpain-1 rescues mitochondrial functions. Similarly, adeno-associated virus 9 (AAV9)-mediated restoration of Erk5 expression in Erk5-CKO hearts prevents cardiomyopathy. These findings suggest that maintaining Erk5 integrity has therapeutic potential for treating metabolic stress-induced cardiomyopathy.The mechanistic link between metabolic stress and associated cardiomyopathy is unknown. Here the authors show that high fat diet causes calpain-1-dependent degradation of ERK5 leading to mitochondrial dysfunction, suggesting the maintenance of cardiac ERK5 as a therapeutic approach for cardiomyopathy prevention and/or treatment.

  5. Numerical simulation of ultrasonic wave propagation in anisotropic and attenuative solid materials

    NASA Astrophysics Data System (ADS)

    You, Zhongqing; Lusk, M.; Ludwig, Reinhold; Lord, William

    1991-09-01

    The axisymmetric elastodynamic finite element code developed is capable of predicting quantitatively accurate displacement fields for elastic wave propagation in isotropic and transversely isotropic materials. The numerical algorithm incorporates viscous damping by adding a time-dependent tensor to Hooke's law. Amplitude comparisons are made between the geometric attenuation in the far field and the corresponding finite element predictions to investigate the quality and validity of the code. Through-transmission experimental measurements made with a 1-MHz L-wave transducer attached to an aluminum sample support the code predictions. The algorithm successfully models geometric beam spreading dispersion and energy absorption due to viscous damping. Extension of the model to include anisotropy, inhomogeneities and the awkward boundaries associated with finite aperture transducers, and realistic defect shapes makes this numerical model a viable tool for the study of elastic wave propagation in nondestructive testing applications.

  6. Anomaly Detection and Artifact Recovery in PET Attenuation-Correction Images Using the Likelihood Function.

    PubMed

    Laymon, Charles M; Bowsher, James E

    2013-02-01

    In dual modality PET/CT, CT data are used to generate the attenuation correction applied in the reconstruction of the PET emission image. This requires converting the CT image into a 511-keV attenuation map. Algorithms for making this transformation require assumptions about the makeup of material within the patient. Anomalous material such as contrast agent administered to enhance the CT scan confounds conversion algorithms and has been observed to result in inaccuracies, i.e., inconsistencies with the true 511-keV attenuation present at the time of the PET emission scan. These attenuation artifacts carry through to the final attenuation-corrected PET emission image and can resemble diseased tissue. We propose an approach to correcting this problem that employs the attenuation information carried by the PET emission data. A likelihood-based algorithm for identifying and correcting of contrast is presented and tested. The algorithm exploits the fact that contrast artifacts manifest as too-high attenuation values in an otherwise high quality attenuation image. In a separate study, the performance of the loglikelihood as an objective-function component of a detection/correction algorithm, independent of any particular algorithm was mapped out for several imaging scenarios as a function of statistical noise. Both the full algorithm and the loglikelihood performed well in studies with simulated data. Additional studies including those with patient data are required to fully understand their capabilities.

  7. Photosensitivity due to thiazides.

    PubMed

    Gómez-Bernal, S; Alvarez-Pérez, A; Rodríguez-Pazos, L; Gutiérrez-González, E; Rodríguez-Granados, M T; Toribio, J

    2014-05-01

    Thiazides are widely used diuretics that first became available in the 1950s. The first reports of photosensitivity reactions to thiazides were published shortly after the introduction of these drugs, but few cases have been described since. We review all the cases of photosensitivity due to thiazides published up to December 2011. We found 62 cases, 33 in women and 29 in men. The most common presentation was eczematous lesions in a photodistributed pattern, and the most common causative agent was hydrochlorothiazide. The results of photobiological studies were published in only some of the cases reviewed. In most cases, phototesting revealed an abnormal response to UV-A alone or to both UV-A and UV-B. In some cases, the results of phototesting were normal and only photopatch testing yielded abnormal results. Diagnosis of photosensitivity due to thiazides requires a high degree of suspicion. Ideally, diagnosis should be confirmed by a photobiological study. Copyright © 2012 Elsevier España, S.L. and AEDV. All rights reserved.

  8. Study of Dual-Wavelength PIA Estimates: Ratio of Ka- and Ku-band Attenuations Obtained from Measured DSD Data

    NASA Astrophysics Data System (ADS)

    Liao, L.; Meneghini, R.; Tokay, A.

    2014-12-01

    generate these profiles fully-, partially- and un-correlated DSD data are employed in an attempt to describe wide dynamic range of microphysical structures of hydrometeors. Bright-band model is employed to take into account of mixed-phase region, and additional attenuations due to cloud water are also included in the profiles.

  9. Microwave Switching and Attenuation with Superconductors.

    NASA Astrophysics Data System (ADS)

    Poulin, Grant Darcy

    1995-01-01

    The discovery of high temperature superconducting (HTS) materials having a critical temperature above the boiling point of liquid nitrogen has generated a large amount of interest in both the basic and applied scientific communities. Considerable research effort has been expended in developing HTS microwave devices, since thin film, passive, microwave components will likely be the first area to be successfully commercialized. This thesis describes a new thin film HTS microwave device that can be operated as a switch or as a continuously variable attenuator. It is well suited for low power analog signal control applications and can easily be integrated with other HTS devices. Due to its small size and mass, the device is expected to find application as a receiver protection switch or as an automatic gain control element, both used in satellite communications receivers. The device has a very low insertion loss, and the isolation in the OFF state is continuously variable to 25 dB. With minor modifications, an isolation exceeding 50 dB is readily achievable. A patent application for the device has been filed, with the patent rights assigned to COM DEV. The device is based on an unusual non-linear response in HTS materials. Under a non-zero DC voltage bias, the current through a superconducting bridge is essentially voltage independent. We have proposed a thermal instability to account for this behaviour. Thermal modelling in conjunction with direct temperature measurements were used to confirm the validity of the model. We have developed a detailed model explaining the microwave response of the device. The model accurately predicts the microwave attenuation as a function of the applied DC control voltage and fully explains the device operation. A key feature is that the device acts as a pure resistive element at microwave frequencies, with no reactance. The resistance is continuously variable, controlled by the DC bias voltage. This distinguishes it from a PIN diode

  10. Relative role of intrinsic and scattering attenuation beneath the Andaman Islands, India and tectonic implications

    NASA Astrophysics Data System (ADS)

    Singh, Chandrani; Biswas, Rahul; Srijayanthi, G.; Ravi Kumar, M.

    2017-10-01

    The attenuation characteristics of seismic waves traversing the Andaman Nicobar subduction zone (ANSZ) are investigated using high quality data from a network of broadband stations operational since 2009. We initially studied the Coda wave attenuation (Qc-1) under the assumption of a single isotropic scattering model. Subsequently, following the multiple isotropic scattering hypothesis, we isolated the relative contributions of intrinsic (Qi-1) and scattering (Qsc-1) attenuation employing the Multiple Lapse Time Window Analysis (MLTWA) method within a frequency range 1.5-18 Hz. Results reveal a highly attenuative nature of the crust, with the values of Qc being frequency dependent. The intrinsic absorption is mostly found to be predominant compared to scattering attenuation. The dominance of Qi-1 in the crust may be attributed to the presence of fluids associated with the subducted slab. Our results are consistent with the low velocity zone reported for the region. A comparison of our results with those from other regions of the globe shows that the ANSZ falls under the category of high intrinsic attenuation zone. Interestingly, the character of ANSZ is identical to that of eastern Himalaya and southern Tibet, but entirely different from the Garhwal-Kumaun Himalaya and the source zone of Chamoli earthquake, due to the underlying mechanisms causing high attenuation.

  11. Efficacy of a Russian-backbone live attenuated influenza vaccine among children in Senegal: a randomised, double-blind, placebo-controlled trial.

    PubMed

    Victor, John C; Lewis, Kristen D C; Diallo, Aldiouma; Niang, Mbayame N; Diarra, Bou; Dia, Ndongo; Ortiz, Justin R; Widdowson, Marc-Alain; Feser, Jodi; Hoagland, Rebecca; Emery, Shannon L; Lafond, Kathryn E; Neuzil, Kathleen M

    2016-12-01

    Live attenuated influenza vaccines have been shown to significantly reduce influenza in diverse populations of children, but no efficacy studies have been done in resource-poor tropical settings. In Senegal, we assessed the efficacy and safety of a live attenuated influenza vaccine based on Russian-derived master donor viruses and licensed as a single dose. In this double-blind, placebo-controlled, parallel group, single-centre trial done near Niakhar, Senegal, generally healthy children aged 2-5 years were randomly allocated (2:1) to receive a single intranasal dose of masked trivalent live attenuated influenza vaccine or placebo. The allocation sequence was computer-generated by PATH with block sizes of three. The manufacturer provided vaccine and placebo in coded vials to preserve blinding. Participants were monitored through the predictable influenza season in Senegal for adverse events and signs and symptoms of influenza using weekly home visits and surveillance in clinics. The primary outcome was symptomatic laboratory-confirmed influenza caused by any strain and occurring from 15 days post-vaccination to the end of the study. The primary analysis was per protocol. This study is registered with ClinicalTrials.gov, number NCT01854632. Between May 23, and July 1, 2013, 1761 children were randomly assigned, 1174 to receive live attenuated influenza vaccine and 587 to receive placebo. The per-protocol set included 1173 vaccinees and 584 placebo recipients followed up to Dec 20, 2013. Symptomatic influenza was laboratory-confirmed in 210 (18%) of 1173 recipients of live attenuated influenza vaccine and 105 (18%) of placebo recipients, giving a vaccine efficacy of 0·0% (95% CI -26·4 to 20·9). Adverse events were balanced between the study groups. Two girls who had received live attenuated influenza vaccine died, one due to anasarca 12 days postvaccination and one due to malnutrition 70 days postvaccination. Live attenuated influenza vaccine was well tolerated in

  12. Hypothermic anesthesia attenuates postoperative proteolysis.

    PubMed Central

    Johnson, D J; Brooks, D C; Pressler, V M; Hulton, N R; Colpoys, M F; Smith, R J; Wilmore, D W

    1986-01-01

    The catabolic response that commonly occurs after major operation is characterized by net skeletal muscle proteolysis and accelerated nitrogen excretion. This response was absent in patients undergoing cardiac surgical procedures associated with the combination of cardiopulmonary bypass, narcotic anesthesia, neuromuscular blockade, and hypothermia. Forearm nitrogen release was 422 +/- 492 nmol/100 ml X min on the first postoperative day, approximately 25% of preoperative values (1677 +/- 411, p less than 0.05). Nitrogen excretion and the degree of negative nitrogen balance were comparable to levels observed in nonstressed, fasting subjects. The potential role of hypothermia, high-dose fentanyl anesthesia, and neuromuscular blockade in modifying the catabolic response to laparotomy and retroperitoneal dissection was further evaluated in animal studies. Six hours after operation, amino acid nitrogen release from the hindquarter was 84% less than control values (p less than 0.05). Nitrogen excretion and urea production were also reduced compared to normothermic controls. It is concluded that the combination of hypothermia, narcotic anesthesia, and neuromuscular blockade attenuates the catabolic response to injury and thus may be useful in the care of critically ill surgical patients. PMID:3767477

  13. Acoustic attenuation analysis program for ducts with mean flow

    NASA Technical Reports Server (NTRS)

    Kunze, R. K., Jr.

    1972-01-01

    A computerized acoustic attenuation prediction procedure has been developed to evaluate acoustically lined ducts for various geometric and environmental parameters. The analysis procedure is based on solutions to the acoustic wave equation, assuming uniform airflow on a duct cross section, combined with appropriate mathematical lining impedance models. The impedance models included in the analysis procedure are representative of either perforated sheet or porous polyimide impregnated fiberglass facing sheet coupled with a cellular backing space. Advantages and limitations of the analysis procedure are reviewed.

  14. A surgical case of frontal lobe epilepsy due to focal cortical dysplasia accompanied by olfactory nerve enlargement: case report.

    PubMed

    Minami, Noriaki; Uda, Takehiro; Matsumoto, Takahiro; Nagai, Taiki; Uchida, Tatsuya; Kamei, Takamasa; Morino, Michiharu

    2014-01-01

    A 45-year-old man came to our clinic due to refractory general tonic seizure and an attack of unintended yelling. Magnetic resonance imaging (MRI) demonstrated mild cortical hyperintensity on fluid attenuated inversion recovery (FLAIR) image in the left basal frontal area. Enlargement of the left olfactory nerve was also detected below the affected gyrus. Subtotal resection of the MRI-visible epileptogenic lesion was performed without any neurological deficit. The final pathological diagnosis was focal cortical dysplasia (FCD) type IIa. Seizures and yelling attacks subsided after surgery. Extracerebral abnormalities, including cranial nerve enlargement, are common in patients with hemimegalencephaly. However, such abnormalities are rare with FCD.

  15. A Surgical Case of Frontal Lobe Epilepsy Due to Focal Cortical Dysplasia Accompanied by Olfactory Nerve Enlargement: Case Report

    PubMed Central

    MINAMI, Noriaki; UDA, Takehiro; MATSUMOTO, Takahiro; NAGAI, Taiki; UCHIDA, Tatsuya; KAMEI, Takamasa; MORINO, Michiharu

    2014-01-01

    A 45-year-old man came to our clinic due to refractory general tonic seizure and an attack of unintended yelling. Magnetic resonance imaging (MRI) demonstrated mild cortical hyperintensity on fluid attenuated inversion recovery (FLAIR) image in the left basal frontal area. Enlargement of the left olfactory nerve was also detected below the affected gyrus. Subtotal resection of the MRI-visible epileptogenic lesion was performed without any neurological deficit. The final pathological diagnosis was focal cortical dysplasia (FCD) type IIa. Seizures and yelling attacks subsided after surgery. Extracerebral abnormalities, including cranial nerve enlargement, are common in patients with hemimegalencephaly. However, such abnormalities are rare with FCD. PMID:24390184

  16. Study of rain attenuation in Ka band for satellite communication in South Korea

    NASA Astrophysics Data System (ADS)

    Shrestha, Sujan; Choi, Dong-You

    2016-10-01

    The important factor to be considered in the link budget estimation for satellite communication systems, operating at frequencies above 10 GHz is the rain attenuation. Scattering and absorption are the main concern for system designers at these frequency bands. This has resulted in the need for suitable prediction models that can best provide estimates of attenuation due to rain with available information of rain attenuation data. Researchers have developed models that can be used to estimate 1-min rainfall attenuation distribution for earth space link but there is still some confusion with regard to choosing the right model to predict attenuation for the location of interest. In this context, the existing prediction models need to be tested against the measured results. This paper presents studies on rain attenuation at 19.8 GHz, which specifies the performance parameters for Ka-Band under earth space communication system. It presents the experimental result of rain rates and rain-induced attenuation in 19.8 and 20.73 GHz for vertical and circular polarization respectively. The received signal data for rain attenuation and rain rate were collected at 10 s intervals over a three year periods from 2013 to 2015. The data highlights the impact of clear air variation and rain fade loss. Rain rate data was measured through OTT Parsivel. During the observation period, rain rates of about 50 mm/h and attenuation values of 11.6 dB for 0.01% of the time were noted. The experimental link was set up at Korea Radio Promotion Association, Mokdong, Seoul. Out of several models, this paper present discussion and comparison of ITU-R P.618-12, Unified Method, Dissanayake Allnutt and Haidara (DAH), Simple Attenuation (SAM), Crane Global and Ramachandran and Kumar models. The relative error margin of 27.51, 89.84,72.46% and 67.24, 130.84, 166.48% are obtained for 0.1%, 0.01% and 0.001% of the time for 19.8 and 20.73 GHz under vertical and circular polarization respectively from ITU

  17. Characterisation of microbial activity in the framework of natural attenuation without groundwater monitoring wells?: a new Direct-Push probe.

    PubMed

    Schurig, Christian; Melo, Vinicio Alejandro; Miltner, Anja; Kaestner, Matthias

    2014-01-01

    At many contaminated field sites in Europe, monitored natural attenuation is a feasible site remediation option. Natural attenuation includes several processes but only the microbial degradation leads to real contaminant removal and very few methods are accepted by the authorities providing real evidence of microbial contaminant degradation activity. One of those methods is the recently developed in situ microcosm approach (BACTRAP®). These in situ microcosms consist of perforated stainless steel cages or PTFE tubes filled with an activated carbon matrix that is amended with 13C-labelled contaminants; the microcosms are then exposed within groundwater monitoring wells. Based on this approach, natural attenuation was accepted by authorities as a site remediation option for the BTEX-polluted site Zeitz in Germany. Currently, the in situ microcosms are restricted to the use inside groundwater monitoring wells at the level of the aquifer. The (classical) system therefore is only applicable on field sites with a network of monitoring wells, and only microbial activity inside the monitoring wells at the level of the aquifer can be assessed. In order to overcome these limitations, a new Direct-Push BACTRAP probe was developed on the basis of the Geoprobe® equipment. With respect to the mechanical boundary conditions of the DP technique, these new probes were constructed in a rugged and segmented manner and are adaptable to various sampling concepts. With this new probe, the approach can be extended to field sites without existing monitoring wells, and microbial activity was demonstrated to be measureable even under very dry conditions inside the vadose zone above the aquifer. In a field test, classical and Direct-Push BACTRAPs were applied in the BTEX-contaminated aquifer at the ModelPROBE reference site Zeitz (Germany). Both types of BACTRAPs were incubated in the centre and at the fringe of the BTEX plume. Analysis of phospholipid fatty acid (PLFA) patterns showed

  18. Natural attenuation software (NAS): Assessing remedial strategies and estimating timeframes

    USGS Publications Warehouse

    Mendez, E.; Widdowson, M.; Chapelle, F.; Casey, C.

    2005-01-01

    Natural Attenuation Software (NAS) is a screening tool to estimate remediation timeframes for monitored natural attenuation (MNA) and to assist in decision-making on the level of source zone treatment in conjunction with MNA using site-specific remediation objectives. Natural attenuation processes that NAS models include are advection, dispersion, sorption, non-aqueous phase liquid (NAPL) dissolution, and biodegradation of either petroleum hydrocarbons or chlorinated ethylenes. Newly-implemented enhancements to NAS designed to maximize the utility of NAS for site managers were observed. NAS has expanded source contaminant specification options to include chlorinated ethanes and chlorinated methanes, and to allow for the analysis of any other user-defined contaminants that may be subject to microbially-mediated transformations (heavy metals, radioisotopes, etc.). Included is the capability to model co-mingled plumes, with constituents from multiple contaminant categories. To enable comparison of remediation timeframe estimates between MNA and specific engineered remedial actions , NAS was modified to incorporate an estimation technique for timeframes associated with pump-and-treat remediation technology for comparison to MNA. This is an abstract of a paper presented at the 8th International In Situ and On-Site Bioremediation Symposium (Baltimore, MD 6/6-9/2005).

  19. Using recombinant DNA technology for the development of live-attenuated dengue vaccines.

    PubMed

    Lee, Hsiang-Chi; Butler, Michael; Wu, Suh-Chin

    2012-07-15

    Dramatic increases in dengue (DEN) incidence and disease severity have been reported, in great part due to the geographic expansion of Aedes aegypti and Aedes albopictus mosquitoes. One result is the expanded co-circulation of all dengue 1-4 serotype viruses (DENV) in urban areas worldwide, especially in South and South-East Asia, and South America. DEN disease severity ranges from asymptomatic infections to febrile dengue fevers (DF) to life-threatening dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). There is an urgent need for a safe and effective tetravalent DEN vaccine. Several live attenuated, tetravalent DEN vaccine candidates have been generated by recombinant DNA technology; these candidates are capable of providing immunity to all four DENV serotypes. In this paper we review (a) recombinant live-attenuated DEN vaccine candidates in terms of deletion, antigen chimerization, and the introduction of adaptive mutations; (b) strategies for improving tetravalent vaccine attenuation; and (c) live-attenuated DENV vaccine development.

  20. Anomalous attenuation of ultrasound in ferrofluids under the influence of a magnetic field

    NASA Technical Reports Server (NTRS)

    Isler, W. E.; Chung, D. Y.

    1978-01-01

    Ultrasonic wave propagation has been studied in a water-base ferrofluid by pulse-echo methods. A commercial box-car integrator was used to measure the change in attenuation due to an external magnetic field applied at various angles relative to the ultrasonic propagation vector. Anomalous results were obtained when the attenuation was plotted as a function of the magnetic field strength. As the field increased, the attenuation reached a maximum and then decreased to a flat minimum before it approached saturation at a field of 2 KG. This variation of attenuation with magnetic field cannot be explained from the simple picture derivable from the work of McTague on the viscosity of ferrofluids. In no case was the viscosity seen to decrease with field, nor was the oscillatory behavior observed. The results of this study were compared with the theory developed by Parsons.

  1. Anomalous attenuation of ultrasound in ferrofluids under the influence of a magnetic field

    NASA Technical Reports Server (NTRS)

    Isler, W. E.; Chung, D. Y.

    1978-01-01

    Ultrasonic wave propagation has been studied in a water-base ferrofluid by pulse-echo methods. A commercial box-car integrator was used to measure the change in attenuation due to an external magnetic field applied at various angles relative to the ultrasonic propagation vector. Anomalous results were obtained when the attenuation was plotted as a function of the magnetic field strength. As the field increased, the attenuation reached a maximum and then decreased to a flat minimum before it approached saturation at a field of 2 KG. This variation of attenuation with magnetic field cannot be explained from the simple picture derivable from the work of McTague on the viscosity of ferrofluids. In no case was the viscosity seen to decrease with field, nor was the oscillatory behavior observed. The results of this study were compared with the theory developed by Parsons.

  2. Continuously tunable fibre attenuator operating in the wavelength range near 1.5 {mu}m

    SciTech Connect

    Baum, Ol'ga I; Mishakov, Gennadii V; Sokolov, Viktor I; Varlamova, Nina V; Zapadinskii, Boris I

    2004-09-30

    A fibre attenuator is fabricated for the telecommunication wavelength range near 1.5 {mu}m in which a single-mode silica fibre with side polishing is used. The fibre surface is covered by a layer of fluorine-containing polymer with a large thermooptic coefficient. The principle of attenuator operation is based on a change in the conditions of total internal reflection for a guided mode in the polished region due to thermally induced variation in the refractive index of the fluoropolymer layer. The attenuator is insensitive to light polarisation, it has a continuously variable attenuation coefficient in the range 0.2-27 dB, and can be easily incorporated into fibreoptic links. (fibre optics)

  3. Thioredoxin Inhibitors Attenuate Platelet Function and Thrombus Formation.

    PubMed

    Metcalfe, Clive; Ramasubramoni, Anjana; Pula, Giordano; Harper, Matthew T; Mundell, Stuart J; Coxon, Carmen H

    2016-01-01

    Thioredoxin (Trx) is an oxidoreductase with important physiological function. Imbalances in the NADPH/thioredoxin reductase/thioredoxin system are associated with a number of pathologies, particularly cancer, and a number of clinical trials for thioredoxin and thioredoxin reductase inhibitors have been carried out or are underway. Due to the emerging role and importance of oxidoreductases for haemostasis and the current interest in developing inhibitors for clinical use, we thought it pertinent to assess whether inhibition of the NADPH/thioredoxin reductase/thioredoxin system affects platelet function and thrombosis. We used small molecule inhibitors of Trx (PMX 464 and PX-12) to determine whether Trx activity influences platelet function, as well as an unbiased proteomics approach to identify potential Trx substrates on the surface of platelets that might contribute to platelet reactivity and function. Using LC-MS/MS we found that PMX 464 and PX-12 affected the oxidation state of thiols in a number of cell surface proteins. Key surface receptors for platelet adhesion and activation were affected, including the collagen receptor GPVI and the von Willebrand factor receptor, GPIb. To experimentally validate these findings we assessed platelet function in the presence of PMX 464, PX-12, and rutin (a selective inhibitor of the related protein disulphide isomerase). In agreement with the proteomics data, small molecule inhibitors of thioredoxin selectively inhibited GPVI-mediated platelet activation, and attenuated ristocetin-induced GPIb-vWF-mediated platelet agglutination, thus validating the findings of the proteomics study. These data reveal a novel role for thioredoxin in regulating platelet reactivity via proteins required for early platelet responses at sites of vessel injury (GPVI and GPIb). This work also highlights a potential opportunity for repurposing of PMX 464 and PX-12 as antiplatelet agents.

  4. Attenuated enzootic (pestoides) isolates of Yersinia pestis express active aspartase.

    PubMed

    Bearden, Scott W; Sexton, Christopher; Pare, Joshua; Fowler, Janet M; Arvidson, Cindy G; Yerman, Lyudmyla; Viola, Ronald E; Brubaker, Robert R

    2009-01-01

    It is established that Yersinia pestis, the causative agent of bubonic plague, recently evolved from enteropathogenic Yersinia pseudotuberculosis by undergoing chromosomal degeneration while acquiring two unique plasmids that facilitate tissue invasion (pPCP) and dissemination by fleabite (pMT). Thereafter, plague bacilli spread from central Asia to sylvatic foci throughout the world. These epidemic isolates exhibit a broad host range including man as opposed to enzootic (pestoides) variants that remain in ancient reservoirs where infection is limited to muroid rodents. Cells of Y. pseudotuberculosis are known to express glucose-6-phosphate dehydrogenase (Zwf) and aspartase (AspA); these activities are not detectable in epidemic Y. pestis due to missense mutations (substitution of proline for serine at amino position 155 of Zwf and leucine for valine at position 363 of AspA). In this study, functional Zwf was found in pestoides strains E, F and G but not seven other enzootic isolates; enzymic activity was associated with retention of serine at amino acid position 155. Essentially, full AspA activity occurred in pestoides isolates where valine (pestoides A, B, C and D) or serine (pestoides E, F, G and I) occupied position 363. Reduced activity occurred in strains Angola and A16, which contained phenylalanine at this position. The kcat but not Km of purified AspA from strain Angola was significantly reduced. In this context, aspA of the recently described attenuated enzootic microtus biovar encodes active valine at position 363, further indicating that functional AspA is a biomarker for avirulence of Y. pestis in man.

  5. Immunization with Eimeria ninakohlyakimovae-live attenuated oocysts protect goat kids from clinical coccidiosis.

    PubMed

    Ruiz, Antonio; Muñoz, María Carmen; Molina, José Manuel; Hermosilla, Carlos; Andrada, Marisa; Lara, Pedro; Bordón, Elisa; Pérez, Davinia; López, Adassa María; Matos, Lorena; Guedes, Aránzazu Carmen; Falcón, Soraya; Falcón, Yaiza; Martín, Sergio; Taubert, Anja

    2014-01-17

    Caprine coccidiosis, affecting mainly young goat kids around the weaning period, is worldwide the most important disease in the goat industry. Control of caprine coccidiosis is increasingly hampered by resistances developed against coccidiostatic drugs leading to an enhanced need for anticoccidial vaccines. In the current study we conducted an oral immunization trial with live attenuated sporulated Eimeria ninakohlyakimovae oocysts. Sporulated E. ninakohlyakimovae oocysts were attenuated by X-irradiation technique. The experimental design included a total of 18 goat kids divided into the following groups: (i) animals immunized with attenuated E. ninakohlyakimovae oocysts at 5 weeks of age and challenged 3 weeks later with non-irradiated homologous oocysts (group 1); (ii) animals infected with non-attenuated E. ninakohlyakimovae oocysts at 5 weeks of age and challenged 3 weeks later with non-attenuated homologous oocysts (group 2); (iii) animals primary-infected with untreated E. ninakohlyakimovae oocysts at 8 weeks of age (control of the challenge infection, group 3); (iv) non-infected control animals (group 4). Goat kids immunized with live attenuated E. ninakohlyakimovae oocysts (group 1) excreted significantly less oocysts in the faeces (95.3% reduction) than kids infected with non-attenuated ones (group 2). Furthermore, immunization with live but attenuated oocysts resulted in ameliorated clinical coccidiosis compared to goat kids infected with untreated oocysts (group 2) and resulted in equally reduced signs of coccidiosis after challenge infection compared to acquired immunity driven by non-attenuated oocysts. Overall, the present study demonstrates for the first time that live attenuated E. ninakohlyakimovae oocysts orally administered showed almost no pathogenicity but enough immunogenicity in terms of immunoprotection. Importantly, vaccinated animals still shed low amounts of oocysts, guaranteeing environmental contamination and consecutive booster

  6. Augmentation of the In Vivo Elastic Properties Measurement System to Include Bulk Properties

    DTIC Science & Technology

    2013-09-30

    system (referred to as “ CFE ”, for Convergent Field Elastography), to include determine bulk tissue speed and attenuation. Such data would provide...measurement system. Bulk speed and attenuation in the 1-3 MHz range will be estimated using transmission and scattering data in the CFE system’s primary...the CFE system force generation transducer. Methods in both frequency ranges will make use of reference measurements made on tissue phantoms whose

  7. Guided wave attenuation in coated pipes buried in sand

    NASA Astrophysics Data System (ADS)

    Leinov, Eli; Cawley, Peter; Lowe, Michael J. S.

    2016-02-01

    Long-range guided wave testing (GWT) is routinely used for the monitoring and detection of corrosion defects in above ground pipelines in various industries. The GWT test range in buried, coated pipelines is greatly reduced compared to aboveground pipelines due to energy leakage into the embedding soil. In this study, we aim to increase test ranges for buried pipelines. The effect of pipe coatings on the T(0,1) and L(0,2) guided wave attenuation is investigated using a full-scale experimental apparatus and model predictions. Tests are performed on a fusion-bonded epoxy (FBE)-coated 8" pipe, buried in loose and compacted sand over a frequency range of 10-35 kHz. The application of a low impedance coating is shown to effectively decouple the influence of the sand on the ultrasound leakage from the buried pipe. We demonstrate ultrasonic isolation of a buried pipe by coating the pipe with a Polyethylene (PE)-foam layer that has a smaller impedance than both pipe and sand and the ability to withstand the overburden load from the sand. The measured attenuation in the buried PE-foam-FBE-coated pipe is substantially reduced, in the range of 0.3-1.2 dBm-1 for loose and compacted sand conditions, compared to buried FBE-coated pipe without the PE-foam, where the measured attenuation is in the range of 1.7-4.7 dBm-1. The acoustic properties of the PE-foam are measured independently using ultrasonic interferometry technique and used in model predictions of guided wave propagation in a buried coated pipe. Good agreement is found between the attenuation measurements and model predictions. The attenuation exhibits periodic peaks in the frequency domain corresponding to the through-thickness resonance frequencies of the coating layer. The large reduction in guided wave attenuation for PE-coated pipes would lead to greatly increased GWT test ranges, so such coatings would be attractive for new pipeline installations.

  8. Neural mechanisms of surround attenuation and distractor competition in visual search.

    PubMed

    Boehler, Carsten N; Tsotsos, John K; Schoenfeld, Mircea A; Heinze, Hans-Jochen; Hopf, Jens-Max

    2011-04-06

    Visual attention biases relevant processing in the visual system by amplifying relevant or attenuating irrelevant sensory input. A potential signature of the latter operation, referred to as surround attenuation, has recently been identified in the electromagnetic brain response of human observers performing visual search. It was found that a zone of attenuated cortical excitability surrounds the target when the search required increased spatial resolution for item discrimination. Here we address the obvious hypothesis that surround attenuation serves distractor suppression in the vicinity of the target where interference from irrelevant search items is maximal. To test this hypothesis, surround attenuation was assessed under conditions when the target was presented in isolation versus when it was surrounded by distractors. Surprisingly, substantial and indistinguishable surround attenuation was seen under both conditions, indicating that it reflects an attentional operation independent of the presence of distractors. Adding distractors in the target's surround, however, increased the amplitude of the N2pc--an evoked response known to index distractor competition in visual search. Moreover, adding distractors led to a topographical change of source activity underlying the N2pc toward earlier extrastriate areas. In contrast, the topography of reduced source activity due to surround attenuation remained unaltered with and without distractors in the target's surround. We conclude that surround attenuation is not a direct consequence of the attenuation of distractors in visual search and that it dissociates from attentional operations reflected by the N2pc. A theoretical framework is proposed that links both operations in a common model of top-down attentional selection in visual cortex.

  9. A Frequency-Shift Method to Measure Shear-Wave Attenuation in Soft Tissues.

    PubMed

    Bernard, Simon; Kazemirad, Siavash; Cloutier, Guy

    2017-03-01

    In vivo quantification of shear-wave attenuation in soft tissues may help to better understand human tissue rheology and lead to new diagnostic strategies. Attenuation is difficult to measure in acoustic radiation force elastography because the shear-wave amplitude decreases due to a combination of diffraction and viscous attenuation. Diffraction correction requires assuming a cylindrical wavefront and an isotropic propagation medium, which may not be the case in some applications. In this paper, the frequency-shift method, used in ultrasound imaging and seismology, was adapted for shear-wave attenuation measurement in elastography. This method is not sensitive to diffraction effects. For a linear frequency dependence of the attenuation, a closed-form relation was obtained between the decrease in the peak frequency of the gamma-distributed wave amplitude spectrum and the attenuation coefficient of the propagation medium. The proposed method was tested against a plane-wave reference method in homogeneous agar-gelatin phantoms with 0%, 10%, and 20% oil concentrations, and hence different attenuations of 0.117, 0.202, and 0.292 [Formula: see text]/Hz, respectively. Applicability to biological tissues was demonstrated with two ex vivo porcine liver samples (0.79 and 1.35 [Formula: see text]/Hz) and an in vivo human muscle, measured along (0.43 [Formula: see text]/Hz) and across (1.77 [Formula: see text]/Hz) the tissue fibers. In all cases, the data supported the assumptions of a gamma-distributed spectrum for the source and linear frequency attenuation for the tissue. This method provides tissue attenuation, which is relevant diagnostic information to model viscosity, in addition to shear-wave velocity used to assess elasticity. Data processing is simple and could be performed automatically in real time for clinical applications.

  10. Direct Reconstruction of CT-based Attenuation Correction Images for PET with Cluster-Based Penalties

    PubMed Central

    Kim, Soo Mee; Alessio, Adam M.; De Man, Bruno; Asma, Evren; Kinahan, Paul E.

    2015-01-01

    Extremely low-dose CT acquisitions for the purpose of PET attenuation correction will have a high level of noise and biasing artifacts due to factors such as photon starvation. This work explores a priori knowledge appropriate for CT iterative image reconstruction for PET attenuation correction. We investigate the maximum a posteriori (MAP) framework with cluster-based, multinomial priors for the direct reconstruction of the PET attenuation map. The objective function for direct iterative attenuation map reconstruction was modeled as a Poisson log-likelihood with prior terms consisting of quadratic (Q) and mixture (M) distributions. The attenuation map is assumed to have values in 4 clusters: air+background, lung, soft tissue, and bone. Under this assumption, the MP was a mixture probability density function consisting of one exponential and three Gaussian distributions. The relative proportion of each cluster was jointly estimated during each voxel update of direct iterative coordinate decent (dICD) method. Noise-free data were generated from NCAT phantom and Poisson noise was added. Reconstruction with FBP (ramp filter) was performed on the noise-free (ground truth) and noisy data. For the noisy data, dICD reconstruction was performed with the combination of different prior strength parameters (β and γ) of Q- and M-penalties. The combined quadratic and mixture penalties reduces the RMSE by 18.7% compared to post-smoothed iterative reconstruction and only 0.7% compared to quadratic alone. For direct PET attenuation map reconstruction from ultra-low dose CT acquisitions, the combination of quadratic and mixture priors offers regularization of both variance and bias and is a potential method to derive attenuation maps with negligible patient dose. However, the small improvement in quantitative accuracy relative to the substantial increase in algorithm complexity does not currently justify the use of mixture-based PET attenuation priors for reconstruction of CT

  11. Shock accelerations and attenuation in downhill and level running.

    PubMed

    Mizrahi, J; Verbitsky, O; Isakov, E

    2000-01-01

    A study was conducted to investigate the possible effects of fatigue on the heel strike-initiated shock accelerations and on attenuation of these shocks along the body during eccentric muscle contractions. Level and decline running on a treadmill were used to acquire the experimental data on the foot strike-initiated shock accelerations. Eccentric contractions of the lower limb muscles in combination with shock generation and propagation during downhill running and muscle fatigue may diminish their ability to dissipate and attenuate loading on the system. Fourteen young healthy males ran on a treadmill at a speed exceeding their anaerobic threshold by 5% for 30 min, as follows: (a) level running and (b) downhill running with a decline angle of -4 degrees. The foot strike-induced shock accelerations were recorded every five minutes on the tibial tuberosity and sacrum. Fatigue was monitored by means of the respiratory parameters. The downhill running related with eccentric muscle contractions was associated with increased shock propagation from the tibial tuberosity to the sacrum levels, even though fatigue did not develop. Shock propagation from the tibial tuberosity to the sacrum is augmented due to the eccentric action of the muscles, without metabolic fatigue development. Eccentric muscle contraction in downhill running reduces the musculoskeletal ability to attenuate the heel strike-induced shock waves. Knowledge about the effect of fatigue on the shock propagation between the shank and the sacrum levels may help in understanding the mechanism of stress fractures and joint damage.

  12. Towards mapping attenuation and water content in the Transition Zone

    NASA Astrophysics Data System (ADS)

    Savage, B. K.

    2013-12-01

    The mantle transition zone is suggested to play a significant role in water storage due to the high solubility of H2O in transition zone minerals. However, quantifying the water content of the transition zone has proven difficult. Previous investigations of the transition zone using a variety of techniques have identified variations in water content globally, associated melt at 400 km, and variable thickness. The resulting water distribution models indicate substantially different Earth models and subsequent seismic responses. Water enhances attenuation with minimal change to seismic wave speed in the transition zone. Taken in combination with correlated temperature induced wave speed / attenuation reductions, the water content and temperature in the transition zone can be inferred. Using upper mantle seismic phases that propagate within the transition zone, we can isolate the effects of attenuation, or anelasticity, and seismic wave speeds. Synthetic seismograms at high frequency, around 1 Hz, from models with a "wet" transition zone show a distinct amplitude reduction and phase delay. Conversely, models with melt on top of the transition zone produce a delayed, secondary arrival with an upper mantle moveout velocity. These diagnostic arrivals, based on synthetic seismic responses, are best identified at the end of the triplicated 660 km branch. Full modeling of the seismic phases from the transition zone will enable a mapping of water content and temperature, while deciphering how water is distributed and transported throughout the mantle.

  13. ATTENUATION OF CORONAL MAGNETIC FIELDS IN SOLAR MICROWAVE BURSTS

    SciTech Connect

    Huang, Guangli; Li, Jianping; Song, Qiwu; Huang, Yu; Tan, Baolin; Wu, Zhao E-mail: jpli@pmo.ac.cn E-mail: songqw@pmo.ac.cn E-mail: wuzhao@sdu.edu.cn

    2015-06-10

    Based on the observed data by the Nobeyama Radio Observatory and the nonthermal gyrosynchrotron theory, the calculated magnetic field in a loop-like radio source of the 2001 October 23 flare attenuates from hundreds to tens of Gauss, except in the region with very weak magnetic fields. Meanwhile, the viewing angle between the magnetic field and line of sight has a similar attenuation from tens to around ten degrees, implying that the transverse magnetic component attenuates much faster than the longitudinal one. All of these results can be understood by the magnetic energy release process in solar flares. Moreover, the column density of nonthermal electrons decreases from 10{sup 9−10} to 10{sup 7−8} cm{sup −2} during the flare, except in the region with very weak magnetic fields, where its value is larger than that with strong magnetic fields due to the mirroring effect. The calculated error and harmonic number of gyrofrequency better suit the region with strong magnetic fields.

  14. A study of the acoustical radiation force considering attenuation

    NASA Astrophysics Data System (ADS)

    Wu, RongRong; Liu, XiaoZhou; Gong, XiuFen

    2013-07-01

    Acoustical tweezer is a primary application of the radiation force of a sound field. When an ultrasound focused beam passes through a micro-particle, like a cell or living biological specimens, the particle will be manipulated accurately without physical contact and invasion, due to the three-dimensional acoustical trapping force. Based on the Ray acoustics approach in the Mie regime, this work discusses the effects on the particle caused by Gaussian focused ultrasound, studies the acoustical trapping force of spherical Mie particles by ultrasound in any position, and analyzes the numerical calculation on the two-dimensional acoustical radiation force. This article also analyzes the conditions for the acoustical trapping phenomenon, and discusses the impact of the initial position and size of the particle on the magnitude of the acoustical radiation force. Furthermore, this paper considers the ultrasonic attenuation in a particle in the case of two-dimension, studies the attenuation's effects on the acoustical trapping force, and amends the calculation to the ordinary case with attenuation.

  15. Genetically attenuated Trypanosoma cruzi parasites as a potential vaccination tool

    PubMed Central

    Brandan, Cecilia Pérez; Basombrío, Miguel Ángel

    2012-01-01

    Chagas disease is the clinical manifestation of the infection produced by the parasite Trypanosoma cruzi. Currently there is no vaccine to prevent this disease and the protection attained with vaccines containing non-replicating parasites is limited. Genetically attenuated trypanosomatid parasites can be obtained by deletion of selected genes. Gene deletion takes advantage of the fact that this parasite can undergo homologous recombination between endogenous and foreign DNA sequences artificially introduced in the cells. This approach facilitated the discovery of several unknown gene functions, as well as allowing us to speculate about the potential for genetically attenuated live organisms as experimental immunogens. Vaccination with live attenuated parasites has been used effectively in mice to reduce parasitemia and histological damage, and in dogs, to prevent vector-delivered infection in the field. However, the use of live parasites as immunogens is controversial due to the risk of reversion to a virulent phenotype. Herein, we present our results from experiments on genetic manipulation of two T. cruzi strains to produce parasites with impaired replication and infectivity, and using the mutation of the dhfr-ts gene as a safety device against reversion to virulence. PMID:22705838

  16. Genetically attenuated Trypanosoma cruzi parasites as a potential vaccination tool.

    PubMed

    Pérez Brandan, Cecilia; Basombrío, Miguel Ángel

    2012-01-01

    Chagas disease is the clinical manifestation of the infection produced by the parasite Trypanosoma cruzi. Currently there is no vaccine to prevent this disease and the protection attained with vaccines containing non-replicating parasites is limited. Genetically attenuated trypanosomatid parasites can be obtained by deletion of selected genes. Gene deletion takes advantage of the fact that this parasite can undergo homologous recombination between endogenous and foreign DNA sequences artificially introduced in the cells. This approach facilitated the discovery of several unknown gene functions, as well as allowing us to speculate about the potential for genetically attenuated live organisms as experimental immunogens. Vaccination with live attenuated parasites has been used effectively in mice to reduce parasitemia and histological damage, and in dogs, to prevent vector-delivered infection in the field. However, the use of live parasites as immunogens is controversial due to the risk of reversion to a virulent phenotype. Herein, we present our results from experiments on genetic manipulation of two T. cruzi strains to produce parasites with impaired replication and infectivity, and using the mutation of the dhfr-ts gene as a safety device against reversion to virulence.

  17. SU-E-T-233: Modeling Linac Couch Effects On Attenuation and Skin Dose

    SciTech Connect

    Xiong, L; Halvorsen, P

    2014-06-01

    Purpose: Treatment couch tops in medical LINAC rooms lead to attenuation to beams penetrating them, plus higher skin dose which can become a significant concern with the high fraction doses associated with Stereotactic Body Radiation Therapy. This work measures the attenuation and shallow depth dose due to a BrainLab couch, and studies the modeling of the couch top in our treatment planning system (TPS) as a uniform solid material with homogeneous density. Methods: LINAC photon beams of size 10×10 cm and nominal energy 6 MV were irradiated from different gantry angles on a stack of solid water. Depth dose were measured with two types of parallel plate chambers, MPPK and Markus. In the Philips Pinnacle TPS, the couch was modeled as a slab with varying thickness and density. A digital phantom of size 30×30×10 cm with density 1 g/cc was created to simulate the measurement setup. Both the attenuation and skin dose effects due to the couch were studied. Results: An orthogonal attenuation rate of 3.2% was observed with both chamber measurements. The attenuation can be modeled by couch models of varying thicknesses. Once the orthogonal attenuation was modeled well, the oblique beam attenuation in TPS agreed with measurement within 1.5%. The depth dose at shallow depth (0.5 cm) was also shown to be modeled correctly within 1.5% of the measurement using a 12 mm thick couch model with density of 0.9 g/cc. Agreement between calculation and measurement diverges at very shallow depths (≤1 mm) but remains acceptable (<5%) with the aforementioned couch model parameters. Conclusion: Modeling the couch top as a uniform solid in a treatment planning system can predict both the attenuation and surface dose simultaneously well within clinical tolerance in the same model.

  18. Measurements And Modeling Of Microbending Attenuation On Spools Wound For Payout

    NASA Astrophysics Data System (ADS)

    Jamieson, John A.; Powell, Rex B.

    1983-03-01

    Attenuation Measurements have been made at 0.82 pm and 1.3 pm on 13 types of monofilament fibers wound on conical payout spools at four levels of pressure. An analytical model of microbending attenuation has been derived by modifying a previous model by Gloge. The measured data fit satisfactorily around the trend predicted by the model. Separate trends are explained for graded index and step index fibers. The influences on attenuation of payout link design parameters including numerical aperture, core, cladding and buffer diameters, spool diameter, winding tension and materials choices are also explained.

  19. Surface Effects due to Subsurface Processes: A Survey

    DTIC Science & Technology

    1982-01-15

    laboratory and field experiments which werc designated to observe the phenomena in wave spjztrd! transfonnation include Wu et al. (1977) and Shemdin et al...for a two-layer coupled-flow model was given by Hsiao and Shemdin (1980) for a finite depth mud layer. 5.1.2.3 Wave Attenuation The direct attenuation...and Shemdin (1978) have investi- gated this problem in detail. 19 5.1.2.5 White-Caps and Wave Breaking It is a well-observed fact that under sustained

  20. Evidence of 1,4-dioxane attenuation at groundwater sites contaminated with chlorinated solvents and 1,4-dioxane.

    PubMed

    Adamson, David T; Anderson, R Hunter; Mahendra, Shaily; Newell, Charles J

    2015-06-02

    There is a critical need to develop appropriate management strategies for 1,4-dioxane (dioxane) due to its widespread occurrence and perceived recalcitrance at groundwater sites where chlorinated solvents are present. A comprehensive evaluation of California state (GeoTracker) and Air Force monitoring records was used to provide significant evidence of dioxane attenuation at field sites. Temporal changes in the site-wide maximum concentrations were used to estimate source attenuation rates at the GeoTracker sites (median length of monitoring period = 6.8 years). While attenuation could not be established at all sites, statistically significant positive attenuation rates were confirmed at 22 sites. At sites where dioxane and chlorinated solvents were present, the median value of all statistically significant dioxane source attenuation rates (equivalent half-life = 31 months; n = 34) was lower than 1,1,1-trichloroethane (TCA) but similar to 1,1-dichloroethene (1,1-DCE) and trichloroethene (TCE). Dioxane attenuation rates were positively correlated with rates for 1,1-DCE and TCE but not TCA. At this set of sites, there was little evidence that chlorinated solvent remedial efforts (e.g., chemical oxidation, enhanced bioremediation) impacted dioxane attenuation. Attenuation rates based on well-specific records from the Air Force data set confirmed significant dioxane attenuation (131 out of 441 wells) at a similar frequency and extent (median equivalent half-life = 48 months) as observed at the California sites. Linear discriminant analysis established a positive correlation between dioxane attenuation and increasing concentrations of dissolved oxygen, while the same analysis found a negative correlation with metals and CVOC concentrations. The magnitude and prevalence of dioxane attenuation documented here suggest that natural attenuation may be used to manage some but not necessarily all dioxane-impacted sites.

  1. A simple rain attenuation model for earth-space radio links operating at 10-35 GHz

    NASA Technical Reports Server (NTRS)

    Stutzman, W. L.; Yon, K. M.

    1986-01-01

    The simple attenuation model has been improved from an earlier version and now includes the effect of wave polarization. The model is for the prediction of rain attenuation statistics on earth-space communication links operating in the 10-35 GHz band. Simple calculations produce attenuation values as a function of average rain rate. These together with rain rate statistics (either measured or predicted) can be used to predict annual rain attenuation statistics. In this paper model predictions are compared to measured data from a data base of 62 experiments performed in the U.S., Europe, and Japan. Comparisons are also made to predictions from other models.

  2. Lg Attenuation Characteristic of Gujarat Region (Western India)

    NASA Astrophysics Data System (ADS)

    Jaiswal, Namrata; Singh, Chandrani

    2016-04-01

    We estimate the Lg attenuation characteristics of the Gujarat Region in Western India by using a reliable two-station method. This region comes under the V, IV and III seismicity zone. So, in India this is the seismic active region other than Himalayas, which shows high seismicity. Lg is typically the most prominent short-period seismic phase on high frequency seismogram observed over the continental paths from regional to teleseimic distance. We use data from 15 earthquakes with magnitude > 5 mb and focal depth < 30 km collected during 2008-2010 from 41 stations deployed in the study region. We estimate 1-Hz Lg Q (Q0) values between many pairs of stations. Finally, 5 events with 70 high-quality inter-station paths were selected from 117 possible pairs of stations that are (1) aligned approximately with the source and (2) separated enough to permit the use of the standard two-station method for Lg Q measurement. Spatial variations in Q0 have been noticed across the Gujarat region. Low Q0 (< 50) values are observed in the Kutch, Jamnagar and southeast region of Gujarat. The northern region of Saurashtra (Gujarat) shows a high Q0 (> 300) value. These observations are consistent with the results of the body wave attenuation structure reported for the region. The variations in the attenuation characteristics may be caused due to both the intrinsic and scattering contributions caused by thermal effects, sedimentary layer thickness as well as heterogeneities present below the study region. Our results are found to be comparable with the previous studies of the attenuation characteristics of the Gujarat region.

  3. Advanced reconstruction of attenuation maps using SPECT emission data only

    NASA Astrophysics Data System (ADS)

    Salomon, André; Goedicke, Andreas; Aach, Til

    2009-02-01

    Today, attenuation corrected SPECT, typically performed using CT or Gadolinium line source based transmission scans, is more and more becoming standard in many medical applications. Moreover, the information about the material density distribution provided by these scans is key for other artifact compensation approaches in advanced SPECT reconstruction. Major drawbacks of these approaches are the additional patient radiation and hardware/maintenance costs as well as the additional workflow effort, e.g. if the CT scans are not performed on a hybrid scanner. It has been investigated in the past, whether it is possible to recover this structural information solely from the SPECT scan data. However, the investigated methods often result in noticeable image artifacts due to cross-dependences between attenuation and activity distribution estimation. With the simultaneous reconstruction method presented in this paper, we aim to effectively prevent these typical cross-talk artifacts using a-priori known atlas information of a human body. At first, an initial 3D shape model is coarsely registered to the SPECT data using anatomical landmarks and each organ structure within the model is identified with its typical attenuation coefficient. During the iterative reconstruction based on a modified ML-EM scheme, the algorithm simultaneously adapts both, the local activity estimation and the 3D shape model in order to improve the overall consistency between measured and estimated sinogram data. By explicitly avoiding topology modifications resulting in a non-anatomical state, we ensure that the estimated attenuation map remains realistic. Several tests with simulated as well as real patient SPECT data were performed to test the proposed algorithm, which demonstrated reliable convergence behaviour in both cases. Comparing the achieved results with available reference data, an overall good agreement for both cold as well as hot activity regions could be observed (mean deviation: -5.98%).

  4. Attenuated retroreflectors for electronic distance measurement

    NASA Astrophysics Data System (ADS)

    Parker, David H.; Goldman, Michael A.; Radcliff, Bill; Shelton, John W.

    Methods are described for attenuating solid glass and hollow retroreflectors, without introducing optical path length modifications, for electronic distance measurement. Construction of a prototype novel-design hollow retroreflector is described.

  5. UHF Radio Wave Attenuation Factor Database

    NASA Astrophysics Data System (ADS)

    Khomenko, S. I.; Kostina, V. L.; Mytsenko, I. M.; Roenko, A. N.

    2007-07-01

    As is known each sea-going vessel is equipped with navigation, communication and other radio engineering facilities that serve to secure the safety of navigation and are chiefly operated at UHF-wave band. In developing these systems and calculating the energy potential for a necessary coverage range one should be well aware of the radio signal attenuation processes on a propagation path. The key parameter of this path is the (radio) wave attenuation factor V and its distance dependence V(R). A diversity of factors influencing the radio signal attenuation over the oceanic expanses, especially well pronounced and quite stable tropospheric ducts, and the lack of experimental data were the compelling reasons why the researchers of the Institute for Radiophysics and Electronics, NASU, had spent many years on comprehensive radiophysical investigations carried out in different regions of the Atlantic, Indian, Arctic and Pacific Oceans. The experimental data obtained allow creating the database of radio wave attenuation factor V.

  6. Attenuation of external Bremsstrahlung in metallic absorbers

    SciTech Connect

    Dhaliwal, A.S.; Powar, M.S.; Singh, M. )

    1990-12-01

    In this paper attenuation of bremsstrahlung from {sup 147}Pm and {sup 170}Tm beta emitters has been studied in aluminum, copper, tin, and lead metallic absorbers. Bremsstrahlung spectra and mass attenuation coefficients for monoenergetic gamma rays are used to calculate theoretical attenuation curves. Magnetic deflection and beta stopping techniques are used to measure the integral bremsstrahlung intensities above 30 keV in different target thicknesses. Comparison of measured and calculated attenuation curves shows a good agreement for various absorbers, thus providing a test of this technique, which may be useful in understanding bremsstrahlung intensity buildup and in the design of optimum shielding for bremsstrahlung sources. It is found that the absorption of bremsstrahlung in metallic absorbers does not obey an exponential law and that absorbers act as energy filters.

  7. Attenuation tomography of the upper inner core

    NASA Astrophysics Data System (ADS)

    Pejić, Tanja; Tkalčić, Hrvoje; Sambridge, Malcolm; Cormier, Vernon F.; Benavente, Roberto

    2017-04-01

    The solidification of the Earth's inner core shapes its texture and rheology, affecting the attenuation and scattering of seismic body waves transmitted through it. Applying attenuation tomography in a Bayesian framework to 398 high-quality PKIKP waveforms, we invert for the apparent Qp for the uppermost 400 km below the inner core boundary at latitudes 45°S to 45°N. We use damping and smoothing for regularization of the inversion, and it seems that the smoothing regularization combined with the discrepancy principle works better for this particular problem of attenuation tomography. The results are consistent with a regional variation in inner core attenuation more complex than hemispherical, suggesting coupling between inner core solidification and the thermal structure of the lowermost mantle.

  8. Enhancing the quality of radiographic images acquired with point-like gamma-ray sources through correction of the beam divergence and attenuation

    NASA Astrophysics Data System (ADS)

    Silvani, M. I.; Almeida, G. L.; Lopes, R. T.

    2014-11-01

    Radiographic images acquired with point-like gamma-ray sources exhibit a desirable low penumbra effects specially when positioned far away from the set object-detector. Such an arrangement frequently is not affordable due to the limited flux provided by a distant source. A closer source, however, has two main drawbacks, namely the degradation of the spatial resolution - as actual sources are only approximately punctual - and the non-homogeneity of the beam hitting the detector, which creates a false attenuation map of the object being inspected. This non-homogeneity is caused by the beam divergence itself and by the different thicknesses traversed the beam even if the object were an homogeneous flat plate. In this work, radiographic images of objects with different geometries, such as flat plates and pipes have undergone a correction of beam divergence and attenuation addressing the experimental verification of the capability and soundness of an algorithm formerly developed to generate and process synthetic images. The impact of other parameters, including source-detector gap, attenuation coefficient, ratio defective-to-main hull thickness and counting statistics have been assessed for specifically tailored test-objects aiming at the evaluation of the ability of the proposed method to deal with different boundary conditions. All experiments have been carried out with an X-ray sensitive Imaging Plate and reactor-produced 198Au and 165Dy sources. The results have been compared with other technique showing a better capability to correct the attenuation map of inspected objects unveiling their inner structure otherwise concealed by the poor contrast caused by the beam divergence and attenuation, in particular for those regions far apart from the vertical of the source.

  9. From Sequential Extraction to Transport Modeling, Monitored Natural Attenuation as a Remediation Approach for Inorganic Contaminants

    SciTech Connect

    POWELL, KIMBERLYR.

    2004-05-25

    Implementation of monitored natural attenuation (MNA) as a remediation method requires a mechanistic understanding of the natural attenuation processes occurring at a given site. For inorganic contaminants, natural attenuation typically involves a decrease in metal toxicity and/or mobility. These natural processes include dilution, dispersion, sorption (including adsorption, absorption, and precipitation), and redox processes. In order to better quantify these processes in terms of metal availability, sequential extraction experiments were carried out on subsurface soil samples impacted by a low pH, high sulfate, metals (Be, Ni, U, As) plume associated with the long-term operation of a coal plant at the Savannah River Site. These laboratory scale studies provide mechanistic information regarding the solid phases in the soils associated with natural attenuation of the contaminant metals. This data provides input to be evaluated in the definition of the contaminant source term as well as transport of contaminants for site transport models.

  10. B-1a Lymphocytes Attenuate Insulin Resistance

    PubMed Central

    Shen, Lei; Chng, MH; Alonso, Michael N.; Yuan, Robert

    2015-01-01

    Obesity-associated insulin resistance, a common precursor of type 2 diabetes, is characterized by chronic inflammation of tissues, including visceral adipose tissue (VAT). Here we show that B-1a cells, a subpopulation of B lymphocytes, are novel and important regulators of this process. B-1a cells are reduced in frequency in obese high-fat diet (HFD)-fed mice, and EGFP interleukin-10 (IL-10) reporter mice show marked reductions in anti-inflammatory IL-10 production by B cells in vivo during obesity. In VAT, B-1a cells are the dominant producers of B cell–derived IL-10, contributing nearly half of the expressed IL-10 in vivo. Adoptive transfer of B-1a cells into HFD-fed B cell–deficient mice rapidly improves insulin resistance and glucose tolerance through IL-10 and polyclonal IgM-dependent mechanisms, whereas transfer of B-2 cells worsens metabolic disease. Genetic knockdown of B cell–activating factor (BAFF) in HFD-fed mice or treatment with a B-2 cell–depleting, B-1a cell–sparing anti-BAFF antibody attenuates insulin resistance. These findings establish B-1a cells as a new class of immune regulators that maintain metabolic homeostasis and suggest manipulation of these cells as a potential therapy for insulin resistance. PMID:25249575

  11. Sulforaphane attenuates EGFR signaling in NSCLC cells.

    PubMed

    Chen, Chi-Yuan; Yu, Zhu-Yun; Chuang, Yen-Shu; Huang, Rui-Mei; Wang, Tzu-Chien V

    2015-06-03

    EGFR, a receptor tyrosine kinase (RTK), is frequently overexpressed and mutated in non-small cell lung cancer (NSCLC). Tyrosine kinase inhibitors (TKIs) have been widely used in the treatment of many cancers, including NSCLC. However, intrinsic and acquired resistance to TKI remains a common obstacle. One strategy that may help overcome EGFR-TKI resistance is to target EGFR for degradation. As EGFR is a client protein of heat-shock protein 90 (HSP90) and sulforaphane is known to functionally regulate HSP90, we hypothesized that sulforaphane could attenuate EGFR-related signaling and potentially be used to treat NSCLC. Our study revealed that sulforaphane displayed antitumor activity against NSCLC cells both in vitro and in vivo. The sensitivity of NSCLC cells to sulforaphane appeared to positively correlate with the inhibition of EGFR-related signaling, which was attributed to the increased proteasomal degradation of EGFR. Combined treatment of NSCLC cells with sulforaphane plus another HSP90 inhibitor (17-AAG) enhanced the inhibition of EGFR-related signaling both in vitro and in vivo. We have shown that sulforaphane is a novel inhibitory modulator of EGFR expression and is effective in inhibiting the tumor growth of EGFR-TKI-resistant NSCLC cells. Our findings suggest that sulforaphane should be further explored for its potential clinical applications against NSCLC.

  12. Attenuation-corrected esophageal transit scintigraphy

    SciTech Connect

    Siegel, J.A.; Brodsky, R.I.; Maurer, A.H.; Fisher, R.S.; Malmud, L.S.

    1985-05-01

    The authors have developed a new method for quantitating regional (R) radionuclide esophageal transit (ET) using attenuation correction (AC) and compared the results with non-AC global ET and manometry in 7 patients (pts). The pts were given 300 ..mu..Ci of Tc-99m sulfur colloid orally and images were acquired every 0.25 sec for 30 sec and then 15 sec for a total of 10 min. The esophagus was divided into six equal regions-of-interest (ROI) for data analysis and curves were generated for each region. A plot of ROI number versus time was generated by using a weighted average of the counts at each individual time point according to /sub i/..sigma.. f/sub i/C/sub i//C/sub t/ where f is the ROI weighting factor, C/sub i/ is the counts in the respective region, and C/sub t/ is the total counts from all regions. AC was then performed by dividing the counts, C/sub i/, by the peak counts for each ROI. Global ET was determined by calculating the percent emptying from the entire esophagus over 10 min during successive 15 sec swallows. Compared to manometry the RET with AC had 100% sensitivity and 100% specificity compared to 50% and 25%, respectively, for non-AC global ET. The authors conclude that RET including AC results in increased sensitivity and specificity for detecting esophogeal dysmotility.

  13. Electron Effective-Attenuation-Length Database

    National Institute of Standards and Technology Data Gateway

    SRD 82 NIST Electron Effective-Attenuation-Length Database (PC database, no charge)   This database provides values of electron effective attenuation lengths (EALs) in solid elements and compounds at selected electron energies between 50 eV and 2,000 eV. The database was designed mainly to provide EALs (to account for effects of elastic-eletron scattering) for applications in surface analysis by Auger-electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS).

  14. Improved efficiency Si-photonic attenuator.

    PubMed

    Zheng, D W; Smith, B T; Asghari, M

    2008-10-13

    A forward-biased p-i-n diode integrated with a ridge waveguide forms a basic Si attenuator building block. Disruptive power improvement was achieved through a recessed contact configuration by limiting the amount of Si volume for carrier recombination. A device model was established by using realistic surface recombination velocities instead of effective carrier lifetime concept to understand the device physics of the afore-mentioned Si attenuator.

  15. Attenuated oncolytic Measles Virus strains as cancer therapeutics

    PubMed Central

    Msaouel, P.; Iankov, I.D.; Dispenzieri, A.; Galanis, E.

    2011-01-01

    Attenuated measles virus vaccine strains have emerged as a promising oncolytic vector platform, having shown significant anti-tumor activity against a broad range of malignant neoplasms. Measles virus strains derived from the attenuated Edmonston-B (MV-Edm) vaccine lineage have been shown to selectively infect, replicate in and lyse cancer cells while causing minimal cytopathic effect on normal tissues. This review summarizes the preclinical data that led to the rapid clinical translation of oncolytic measles vaccine strains and provides an overview of early clinical data using this oncolytic platform. Furthermore, novel approaches currently under development to further enhance the oncolytic efficacy of MV-Edm strains, including strategies to circumvent immunity or modulate immune system responses, combinatorial approaches with standard treatment modalities, virus retargeting as well as strategies for in vivo monitoring of viral replication are discussed. PMID:21740361

  16. Amplification, attenuation, and dispersion of sound in inhomogeneous flows

    NASA Technical Reports Server (NTRS)

    Kentzer, C. P.

    1975-01-01

    First order effects of gradients in nonuniform potential flows of a compressible gas are included in a dispersion relation for sound waves. Three nondimensional numbers, the ratio of the change in the kinetic energy in one wavelength to the thermal energy of the gas, the ratio of the change in the total energy in one wavelength to the thermal energy, and the ratio of the dillatation frequency (the rate of expansion per unit volume) to the acoustic frequency, play a role in the separation of the effects of flow gradients into isotropic and anisotropic effects. Dispersion and attenuation (or amplification) of sound are found to be proportional to the wavelength for small wavelength, and depend on the direction of wave propagation relative to flow gradients. Modification of ray acoustics for the effects of flow gradients is suggested, and conditions for amplification and attenuation of sound are discussed.

  17. Ultrasonic attenuation - Q measurements on 70215,29. [lunar rock

    NASA Technical Reports Server (NTRS)

    Warren, N.; Trice, R.; Stephens, J.

    1974-01-01

    Ultrasonic attenuation measurements have been made on an aluminum alloy, obsidian, and rock samples including lunar sample 70215,29. The measurement technique is based on a combination of the pulse transmission method and the forced resonance method. The technique is designed to explore the problem of defining experimentally, the Q of a medium or sample in which mode conversion may occur. If modes are coupled, the measured attenuation is strongly dependent on individual modes of vibration, and a range of Q-factors may be measured over various resonances or from various portions of a transient signal. On 70215,29, measurements were made over a period of a month while the sample outgassed in hard varuum. During this period, the highest measured Q of this sample increased from a few hundred into the range of 1000-1300.

  18. Ultrasonic attenuation - Q measurements on 70215,29. [lunar rock

    NASA Technical Reports Server (NTRS)

    Warren, N.; Trice, R.; Stephens, J.

    1974-01-01

    Ultrasonic attenuation measurements have been made on an aluminum alloy, obsidian, and rock samples including lunar sample 70215,29. The measurement technique is based on a combination of the pulse transmission method and the forced resonance method. The technique is designed to explore the problem of defining experimentally, the Q of a medium or sample in which mode conversion may occur. If modes are coupled, the measured attenuation is strongly dependent on individual modes of vibration, and a range of Q-factors may be measured over various resonances or from various portions of a transient signal. On 70215,29, measurements were made over a period of a month while the sample outgassed in hard varuum. During this period, the highest measured Q of this sample increased from a few hundred into the range of 1000-1300.

  19. Numerical support of laboratory experiments: Attenuation and velocity estimations

    NASA Astrophysics Data System (ADS)

    Saenger, Erik; Madonna, Claudio; Frehner, Marcel; Almqvist, Bjarne

    2014-02-01

    We show that numerical support of laboratory experiments can significantly increase the understanding and simplify the interpretation of the obtained laboratory results. First we perform simulations of the Seismic Wave Attenuation Module to measure seismic attenuation of reservoir rocks. Our findings confirm the accuracy of this system. However, precision can be further improved by optimizing the sensor positions. Second, we model wave propagation for an ultrasonic pulse transmission experiment used to determine pressure- and temperature-dependent seismic velocities in the rock. Multiple waves are identified in our computer experiment, including bar waves. The metal jacket that houses the sample assembly needs to be taken into account for a proper estimation of the ultrasonic velocities. This influence is frequency-dependent.

  20. Sensory Attenuation for Jointly Produced Action Effects

    PubMed Central

    Loehr, Janeen D.

    2012-01-01

    Successful joint action often requires people to distinguish between their own and others’ contributions to a shared goal. One mechanism that is thought to underlie a self-other distinction is sensory attenuation, whereby the sensory consequences of one’s own actions are reduced compared to other sensory events. Previous research has shown that the auditory N1 event-related potential (ERP) response is reduced for self-generated compared to externally generated tones. The current study examined whether attenuation also occurs for jointly generated tones, which require two people to coordinate their actions to produce a single tone. ERP responses were measured when participants generated tones alone (tone onset immediately followed the participant’s button press) or with a partner (tone onset immediately followed the participant’s or the partner’s button press, whichever occurred second). N1 attenuation was smaller for jointly generated tones compared to self-generated tones. For jointly generated tones, greater delays between the participant’s and the partner’s button presses were associated with reduced attenuation; moreover, only trials in which there was no delay between the participant’s press and tone onset showed attenuation, whereas trials in which there were delays did not show attenuation. These findings indicate that people differentiate between their own and another person’s contributions to a joint action at the sensorimotor level, even when they must act together to produce a single, shared effect. PMID:23596429

  1. Ursodeoxycholic acid attenuates colonic epithelial secretory function

    PubMed Central

    Kelly, Orlaith B; Mroz, Magdalena S; Ward, Joseph B J; Colliva, Carolina; Scharl, Michael; Pellicciari, Roberto; Gilmer, John F; Fallon, Padraic G; Hofmann, Alan F; Roda, Aldo; Murray, Frank E; Keely, Stephen J

    2013-01-01

    Dihydroxy bile acids, such as chenodeoxycholic acid (CDCA), are well known to promote colonic fluid and electrolyte secretion, thereby causing diarrhoea associated with bile acid malabsorption. However, CDCA is rapidly metabolised by colonic bacteria to ursodeoxycholic acid (UDCA), the effects of which on epithelial transport are poorly characterised. Here, we investigated the role of UDCA in the regulation of colonic epithelial secretion. Cl− secretion was measured across voltage-clamped monolayers of T84 cells and muscle-stripped sections of mouse or human colon. Cell surface biotinylation was used to assess abundance/surface expression of transport proteins. Acute (15 min) treatment of T84 cells with bilateral UDCA attenuated Cl− secretory responses to the Ca2+ and cAMP-dependent secretagogues carbachol (CCh) and forskolin (FSK) to 14.0 ± 3.8 and 40.2 ± 7.4% of controls, respectively (n= 18, P < 0.001). Investigation of the molecular targets involved revealed that UDCA acts by inhibiting Na+/K+-ATPase activity and basolateral K+ channel currents, without altering their cell surface expression. In contrast, intraperitoneal administration of UDCA (25 mg kg−1) to mice enhanced agonist-induced colonic secretory responses, an effect we hypothesised to be due to bacterial metabolism of UDCA to lithocholic acid (LCA). Accordingly, LCA (50–200 μm) enhanced agonist-induced secretory responses in vitro and a metabolically stable UDCA analogue, 6α-methyl-UDCA, exerted anti-secretory actions in vitro and in vivo. In conclusion, UDCA exerts direct anti-secretory actions on colonic epithelial cells and metabolically stable derivatives of the bile acid may offer a new approach for treating intestinal diseases associated with diarrhoea. PMID:23507881

  2. Family Living, Including Sex Education.

    ERIC Educational Resources Information Center

    Forlano, George

    This volume describes and evaluates 21 selected New York City Board of Education Umbrella Programs for the 1974-1975 school year. The programs include: (1) the parent resource center, (2) the teacher self-help program, (3) the East Harlem pre-kindergarten center, (4) the Brooklyn College volunteer tutoring program, (5) the parent education for…

  3. High-frequency magnetic properties and attenuation characteristics for barium ferrite composites

    NASA Astrophysics Data System (ADS)

    Li, Z. W.; Lin, G. Q.; Wu, Y. P.; Kong, L. B.

    2009-04-01

    High-frequency magnetic properties and attenuation characteristics for barium-ferrite/epoxy composites have been studied. The methods for increasing μ' and μ″ and controlling fR, including ion substitution, doping of small amount of oxides, effect of damping, as well as the modification of particle sizes and shapes, are introduced. The results show that the composites are potential candidates for use as electromagnetic (EM) attenuation materials with low reflectivity and broad bandwidth at 2-18 GHz.

  4. The thermal structure of cratonic lithosphere from global Rayleigh wave attenuation

    NASA Astrophysics Data System (ADS)

    Dalton, Colleen A.; Bao, Xueyang; Ma, Zhitu

    2017-01-01

    The resolution of and level of agreement between different attenuation models have historically been limited by complexities associated with extracting attenuation from seismic-wave amplitudes, which are also affected by the source, the receiver, and propagation through velocity heterogeneities. For intermediate- and long-period Rayleigh waves, removing the amplitude signal due to focusing and defocusing effects is the greatest challenge. In this paper, three independent data sets of fundamental-mode Rayleigh wave amplitude are analyzed to investigate how three factors contribute to discrepancies between the attenuation models: uncertainties in the amplitude measurements themselves, variable path coverage, and the treatment of focusing effects. Regionalized pure-path and fully two-dimensional attenuation models are derived and compared. The approach for determining attenuation models from real data is guided by an analysis of amplitudes measured from synthetic spectral-element waveforms, for which the input Earth model is perfectly known. The results show that differences in the amplitude measurements introduce only very minor differences between the attenuation models; path coverage and the removal of focusing effects are more important. The pure-path attenuation values exhibit a clear dependence on tectonic region at shorter periods that disappears at long periods, in agreement with pure-path phase-velocity results obtained by inverting Rayleigh wave phase delays. The 2-D attenuation maps are highly correlated with each other to spherical-harmonic degree 16 and can resolve smaller features than the previous generation of global attenuation models. Anomalously low attenuation is nearly perfectly associated with continental cratons. Variations in lithospheric thickness are determined by forward modeling the global attenuation variations as a thermal boundary layer of variable thickness. Temperature profiles that satisfy the attenuation values systematically

  5. The ultraviolet attenuation law in backlit spiral galaxies

    SciTech Connect

    Keel, William C.; Manning, Anna M.; Holwerda, Benne W.; Lintott, Chris J.; Schawinski, Kevin E-mail: ammanning@bama.ua.edu E-mail: Twitter@BenneHolwerda E-mail: Twitter@chrislintott E-mail: Twitter@kevinschawinski

    2014-02-01

    The effective extinction law (attenuation behavior) in galaxies in the emitted ultraviolet (UV) regime is well known only for actively star-forming objects and combines effects of the grain properties, fine structure in the dust distribution, and relative distributions of stars and dust. We use Galaxy Evolution Explorer, XMM Optical Monitor, and Hubble Space Telescope (HST) data to explore the UV attenuation in the outer parts of spiral disks which are backlit by other UV-bright galaxies, starting with the candidate list of pairs provided by Galaxy Zoo participants. New optical images help to constrain the geometry and structure of the target galaxies. Our analysis incorporates galaxy symmetry, using non-overlapping regions of each galaxy to derive error estimates on the attenuation measurements. The entire sample has an attenuation law across the optical and UV that is close to the Calzetti et al. form; the UV slope for the overall sample is substantially shallower than found by Wild et al., which is a reasonable match to the more distant galaxies in our sample but not to the weighted combination including NGC 2207. The nearby, bright spiral NGC 2207 alone gives an accuracy almost equal to the rest of our sample, and its outer arms have a very low level of foreground starlight. Thus, this widespread, fairly 'gray' law can be produced from the distribution of dust alone, without a necessary contribution from differential escape of stars from dense clouds. Our results indicate that the extrapolation needed to compare attenuation between backlit galaxies at moderate redshifts from HST data, and local systems from Sloan Digital Sky Survey and similar data, is mild enough to allow the use of galaxy overlaps to trace the cosmic history of dust in galaxies. For NGC 2207, HST data in the near-UV F336W band show that the covering factor of clouds with small optical attenuation becomes a dominant factor farther into the UV, which opens the possibility that widespread

  6. The Ultraviolet Attenuation Law in Backlit Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Keel, William C.; Manning, Anna M.; Holwerda, Benne W.; Lintott, Chris J.; Schawinski, Kevin

    2014-02-01

    The effective extinction law (attenuation behavior) in galaxies in the emitted ultraviolet (UV) regime is well known only for actively star-forming objects and combines effects of the grain properties, fine structure in the dust distribution, and relative distributions of stars and dust. We use Galaxy Evolution Explorer, XMM Optical Monitor, and Hubble Space Telescope (HST) data to explore the UV attenuation in the outer parts of spiral disks which are backlit by other UV-bright galaxies, starting with the candidate list of pairs provided by Galaxy Zoo participants. New optical images help to constrain the geometry and structure of the target galaxies. Our analysis incorporates galaxy symmetry, using non-overlapping regions of each galaxy to derive error estimates on the attenuation measurements. The entire sample has an attenuation law across the optical and UV that is close to the Calzetti et al. form; the UV slope for the overall sample is substantially shallower than found by Wild et al., which is a reasonable match to the more distant galaxies in our sample but not to the weighted combination including NGC 2207. The nearby, bright spiral NGC 2207 alone gives an accuracy almost equal to the rest of our sample, and its outer arms have a very low level of foreground starlight. Thus, this widespread, fairly "gray" law can be produced from the distribution of dust alone, without a necessary contribution from differential escape of stars from dense clouds. Our results indicate that the extrapolation needed to compare attenuation between backlit galaxies at moderate redshifts from HST data, and local systems from Sloan Digital Sky Survey and similar data, is mild enough to allow the use of galaxy overlaps to trace the cosmic history of dust in galaxies. For NGC 2207, HST data in the near-UV F336W band show that the covering factor of clouds with small optical attenuation becomes a dominant factor farther into the UV, which opens the possibility that widespread

  7. General presentation including new structure

    NASA Astrophysics Data System (ADS)

    Soons, A.

    2002-12-01

    Electrical, electronic and electro-mechanical components play an essential role in the functional performance, quality, life cycle and costs of space systems. Their standardisation, product specification, development, evaluation, qualification and procurement must be based on a coherent and efficient approach, paying due attention to present and prospective European space policies and must be commensurate with user needs, market developments and technology trends. The European Space Components Coordination (ESCC) is established with the objective of harmonising the efforts concerning the various aspects of EEE space components by ESA. European national and international public space organisations, the component manufacturers and the user industries. The goal of the ESCC is to improve the availability of strategic EEE space components with the required performance and at affordable costs for institutional and commercial space programmes. It is the objective of ESCC to achieve this goal by harmonising the resources and development efforts for space components in the ESA Member States and by providing a single and unified system for the standardisation, product specification, evaluation, qualification and procurement of European EEE space components and for the certification of components and component manufacturers.

  8. Attenuation of Oxidative Stress in HEK 293 Cells by the TCM Constituents Schisanhenol, Baicalein, Resveratrol or Crocetin and Two Defined Mixtures.

    PubMed

    Bend, John Richard; Xia, Xue Yan; Chen, Daofeng; Awaysheh, Abudi; Lo, Andrea; Rieder, Michael John; Rylett, Rebecca Jane

    2015-01-01

    Our working hypothesis is that single bioactive phytochemicals with antioxidant properties that are important constituents of Traditional Chinese Medicine (TCM) and their defined mixtures have potential as chemoprotective agents for chronic conditions characterized by oxidative and nitrosative stress, including Alzheimer's. Here we evaluate the ability of baicalein, crocetin, trans-resveratrol or schisanhenol and two defined mixtures of these TCM phytochemicals to attenuate the toxicity resulting from exposure to cell permeant t-butyl hydroperoxide (tBPH) in wild-type and bioengineered (to express choline acetyltransferase) HEK 293 cells. Endpoints of tBHP-initiated oxidative and nitrosative stress in both types of HEK 293 cells and its attenuation by TCM constituents and mixtures included cytotoxicity (LDH release); depletion of intracellular glutathione (GSH); formation of S-glutathionylated proteins; oxidative changes to the disulfide proteome; and real-time changes in intracellular redox status. At low µM concentrations, each of the TCM constituents and mixtures effectively attenuated intracellular toxicity due to exposure of HEK 293 cells to 50 or 250 µM tBHP for 30 min to 3 h. Confocal microscopy of HEK 293 cells transfected with mutated green fluorescent protein (roGFP2) showed effective attenuation of tBHP oxidation by baicalein in real time. Three redox-regulated proteins prominent in the disulfide proteome of HEK 293 cells were identified by MALDI-TOF mass spectrometry. We conclude that single TCM chemicals and their simple mixtures have potential for use in adjunct chemoprotective therapy. Advantages of mixtures compared to single TCM constituents include the ability to combine compounds with varying molecular mechanisms of cytoprotection for enhanced biological activity; and to combine chemicals with complementary pharmacokinetic properties to increase half-life and prolong activity in vivo. This article is open to POST-PUBLICATION REVIEW. Registered

  9. Study of transmission line attenuation in broad band millimeter wave frequency range

    SciTech Connect

    Pandya, Hitesh Kumar B.; Austin, M. E.; Ellis, R. F.

    2013-10-15

    Broad band millimeter wave transmission lines are used in fusion plasma diagnostics such as electron cyclotron emission (ECE), electron cyclotron absorption, reflectometry and interferometry systems. In particular, the ECE diagnostic for ITER will require efficient transmission over an ultra wide band, 100 to 1000 GHz. A circular corrugated waveguide transmission line is a prospective candidate to transmit such wide band with low attenuation. To evaluate this system, experiments of transmission line attenuation were performed and compared with theoretical loss calculations. A millimeter wave Michelson interferometer and a liquid nitrogen black body source are used to perform all the experiments. Atmospheric water vapor lines and continuum absorption within this band are reported. Ohmic attenuation in corrugated waveguide is very low; however, there is Bragg scattering and higher order mode conversion that can cause significant attenuation in this transmission line. The attenuation due to miter bends, gaps, joints, and curvature are estimated. The measured attenuation of 15 m length with seven miter bends and eighteen joints is 1 dB at low frequency (300 GHz) and 10 dB at high frequency (900 GHz), respectively.

  10. Application of discrete data consistency conditions for selecting regularization parameters in PET attenuation map reconstruction.

    PubMed

    Panin, Vladimir Y; Kehren, Frank; Hamill, James J; Michel, Christian

    2004-06-07

    Simultaneous emission and transmission measurement is appealing in PET due to the matching of geometrical conditions between emission and transmission and reduced acquisition time for the study. A potential problem remains: when transmission statistics are low, attenuation correction could be very noisy. Although noise in the attenuation map can be controlled through regularization during statistical reconstruction, the selection of regularization parameters is usually empirical. In this paper, we investigate the use of discrete data consistency conditions (DDCC) to optimally select one or two regularization parameters. The advantages of the method are that the reconstructed attenuation map is consistent with the emission data and that it accounts for particularity in the emission reconstruction algorithm and acquisition geometry. The methodology is validated using a computer-generated whole-body phantom for both emission and transmission, neglecting random events and scattered radiation. MAP-TR was used for attenuation map reconstruction, while 3D OS-EM is used for estimating the emission image. The estimation of regularization parameters depends on the resolution of the emission image controlled by the number of iterations in OS-EM. The computer simulation shows that, on one hand, DDCC regularized attenuation map reduces propagation of the transmission scan noise to the emission image, while on the other hand DDCC prevents excessive attenuation map smoothing that could result in resolution mismatch artefacts between emission and transmission.

  11. Measurement of alkali-silica reaction progression by ultrasonic waves attenuation

    SciTech Connect

    Saint-Pierre, Francois; Rivard, Patrice . E-mail: Patrice.Rivard@Usherbrooke.ca; Ballivy, Gerard

    2007-06-15

    Development of non-destructive methods, developed specifically for assessing the damage induced by alkali-silica reaction (ASR) in concrete structures, is needed in order to carry out a systematic evaluation of the concrete condition. The aim of this study is to monitor the evolution of the ASR-damage in laboratory with concrete samples with ultrasonic pulse velocity and attenuation of ultrasonic waves methods. For this study, results of both methods were compared with expansion and mass variation. One reactive concrete mixture was made with reactive aggregate, and one other mixture, incorporating non-reactive aggregate, was made as a control. Specimens were kept at 38 deg. C in a 1 mol l{sup -1} NaOH solution to accelerate the reaction. Attenuation of transmitted ultrasonic waves appeared to be more appropriate for the evaluation of ASR-damage compared with pulse velocity. The attenuation of accelerated reactive concrete cylinders increased by 90% after 1 year while it increased by 40% for the non-reactive concrete used as a control. Major part of the attenuation increase in the non-reactive concrete is due to liquid absorption. This work suggests that in-situ non-destructive techniques based on ultrasonic wave attenuation, like ultrasonic attenuation tomography, should be developed in order to evaluate the development of ASR in concrete structures. Petrographic examination confirmed that damage to concrete is associated with ASR.

  12. Imaging fluid-related subduction processes beneath Central Java (Indonesia) using seismic attenuation tomography

    NASA Astrophysics Data System (ADS)

    Bohm, Mirjam; Haberland, Christian; Asch, Günter

    2013-04-01

    We use local earthquake data observed by the amphibious, temporary seismic MERAMEX array to derive spatial variations of seismic attenuation (Qp) in the crust and upper mantle beneath Central Java. The path-averaged attenuation values (t∗) of a high quality subset of 84 local earthquakes were calculated by a spectral inversion technique. These 1929 t∗-values inverted by a least-squares tomographic inversion yield the 3D distribution of the specific attenuation (Qp). Analysis of the model resolution matrix and synthetic recovery tests were used to investigate the confidence of the Qp-model. We notice a prominent zone of increased attenuation beneath and north of the modern volcanic arc at depths down to 15 km. Most of this anomaly seems to be related to the Eocene-Miocene Kendeng Basin (mainly in the eastern part of the study area). Enhanced attenuation is also found in the upper crust in the direct vicinity of recent volcanoes pointing towards zones of partial melts, presence of fluids and increased temperatures in the middle to upper crust. The middle and lower crust seems not to be associated with strong heating and the presence of melts throughout the arc. Enhanced attenuation above the subducting slab beneath the marine forearc seems to be due to the presence of fluids.

  13. Seismic Attenuation beneath Tateyama Volcano, Central Japan

    NASA Astrophysics Data System (ADS)

    Iwata, K.; Kawakata, H.; Doi, I.

    2014-12-01

    Subsurface structures beneath active volcanoes have frequently been investigated (e.g., Oikawa et al., 1994: Sudo et al., 1996), and seismic attenuation beneath some active volcanoes are reported to be strong. On the other hand, few local subsurface structures beneath volcanoes whose volcanic activities are low have been investigated in detail, though it is important to study them to understand the potential of volcanic activity of these volcanoes. Then, we analyzed the seismic attenuation beneath Tateyama volcano (Midagahara volcano) located in central Japan, whose volcanic activity is quite low. We used seismograms obtained by Hi-net deployed by NIED (National Research Institute for Earth Science and Disaster Prevention). Hi-net is one of the densest seismic station networks in the world, and the spatial interval of their seismographs is about 20 km, which is suitable for investigating local structure beneath an individual volcano. We estimated S-wave attenuation using seismograms at five stations near Tateyama volcano for nineteen small, local, shallow earthquakes (M 2.7-4.0) that occurred from January 2012 to December 2013. We divided these earthquakes into six groups according to their hypocenter locations. We used twofold spectral ratios around the first S-arrivals to investigate the S-wave attenuation when S-waves passed through the region beneath Tateyama volcano. We focused on station pairs located on opposite sides of Tateyama volcano to each other, and earthquake pairs whose epicenters were located almost along the line connecting Tateyama volcano and the two stations, so that the spectral ratios reflect a local structure beneath Tateyama volcano. Twofold spectral ratios of all seismograms for S waves having northwestern or southeastern sources show strong attenuation beneath Tateyama volcano. On the other hand, those of seismograms having northeastern or southwestern sources show much weaker attenuation, which suggested that the region of strong

  14. Phase Aberration and Attenuation Effects on Acoustic Radiation Force-Based Shear Wave Generation.

    PubMed

    Carrascal, Carolina Amador; Aristizabal, Sara; Greenleaf, James F; Urban, Matthew W

    2016-02-01

    Elasticity is measured by shear wave elasticity imaging (SWEI) methods using acoustic radiation force to create the shear waves. Phase aberration and tissue attenuation can hamper the generation of shear waves for in vivo applications. In this study, the effects of phase aberration and attenuation in ultrasound focusing for creating shear waves were explored. This includes the effects of phase shifts and amplitude attenuation on shear wave characteristics such as shear wave amplitude, shear wave speed, shear wave center frequency, and bandwidth. Two samples of swine belly tissue were used to create phase aberration and attenuation experimentally. To explore the phase aberration and attenuation effects individually, tissue experiments were complemented with ultrasound beam simulations using fast object-oriented C++ ultrasound simulator (FOCUS) and shear wave simulations using finite-element-model (FEM) analysis. The ultrasound frequency used to generate shear waves was varied from 3.0 to 4.5 MHz. Results: The measured acoustic pressure and resulting shear wave amplitude decreased approximately 40%-90% with the introduction of the tissue samples. Acoustic intensity and shear wave displacement were correlated for both tissue samples, and the resulting Pearson's correlation coefficients were 0.99 and 0.97. Analysis of shear wave generation with tissue samples (phase aberration and attenuation case), measured phase screen, (only phase aberration case), and FOCUS/FEM model (only attenuation case) showed that tissue attenuation affected the shear wave generation more than tissue aberration. Decreasing the ultrasound frequency helped maintain a focused beam for creation of shear waves in the presence of both phase aberration and attenuation.

  15. Mapping of attenuating sequences of an avirulent poliovirus type 2 strain.

    PubMed

    Moss, E G; O'Neill, R E; Racaniello, V R

    1989-05-01

    A mouse model for poliomyelitis was used to identify genomic sequences that attenuate neurovirulence of poliovirus strain P2/P712. This type 2 strain is avirulent in primates and mice yet grows as well as virulent strains in cell culture. The approach used was to exchange portions of the genome of the mouse-virulent P2/Lansing strain with the corresponding region from P2/P712 to identify sequences that could attenuate Lansing neurovirulence in mice. A full-length infectious cDNA of P2/P712 was assembled and used to construct recombinants between P2/P712 and P2/Lansing. The results of neurovirulence testing of 11 recombinants indicated that strong attenuating determinants are located in the 5' noncoding region of P2/P712 and a region encoding capsid protein VP1 and 2Apro, 2B, and part of 2C. An attenuating determinant was further localized to between nucleotides 456 and 628 of P2/P712. A third sequence from P2/P712, nucleotides 752 to 2268, encoding VP4, VP2, and part of VP3, was weakly attenuating. The sequence from nucleotide 4454, approximately halfway through the 2C-coding region, to the end of the P2/P712 genome did not contain attenuating determinants. Nucleotide sequence analysis revealed that P2/P712 differs from the type 2 Sabin vaccine strain by only 22 nucleotides. Six differences lead to amino acid changes in the coding region, and four differences are in the 5' noncoding region. These studies show that, like the type 1 and type 3 Sabin vaccine strains, the attenuated type 2 strain P712 contains multiple attenuating sequences, including strongly attenuating sequences in the 5' noncoding region of the genome.

  16. Phase Aberration and Attenuation Effects on Acoustic Radiation Force-Based Shear Wave Generation

    PubMed Central

    Amador, Carolina; Aristizabal, Sara; Greenleaf, James F.; Urban, Matthew W.

    2016-01-01

    Tissue elasticity is measured by shear wave elasticity imaging methods using acoustic radiation force to create the shear waves. Phase aberration and tissue attenuation can hamper the generation of shear waves for in vivo applications. In this study effects of phase aberration and attenuation in ultrasound focusing for creating shear waves were explored. This includes the effects of phase shifts and amplitude attenuation on shear wave characteristics such as shear wave amplitude, shear wave speed, shear wave center frequency and bandwidth. Two samples of swine belly tissue were used to create phase aberration and attenuation experimentally. To explore the phase aberration and attenuation effects individually, tissue experiments were complemented with ultrasound beam simulations using FOCUS and shear wave simulations using Finite Element Model (FEM) analysis. The ultrasound frequency used to generate shear waves was varied from 3.0 to 4.5 MHz. Results The measured acoustic pressure and resulting shear wave amplitude decreased approximately 40% to 90% with the introduction of the tissue samples. Acoustic intensity and shear wave displacement were correlated for both tissue samples, the resulting Pearson’s correlation coefficients were 0.99 and 0.97. Analysis of shear wave generation with tissue samples (Phase Aberration and Attenuation case), measured phase screen (Only Phase Aberration case) and FOCUS/FEM model (Only Attenuation case) showed that tissue attenuation affected the shear wave generation more than tissue aberration. Decreasing the ultrasound frequency helped maintain a focused beam for creation of shear waves in the presence of both phase aberration and attenuation. PMID:26742131

  17. Termination of Faculty due to Financial Exigency.

    ERIC Educational Resources Information Center

    Holloway, John P.

    1980-01-01

    Recent court cases involving termination of faculty due to financial exigency are summarized. Sections include an introduction, definition, a survey of recent cases, recommendations, conclusions and questions, and a bibliography. (Author/LC)

  18. Estimate of the attenuation coefficient using a clinical array transducer for the detection of cervical ripening in human pregnancy

    PubMed Central

    Labyed, Yassin; Bigelow, Timothy A.; McFarlin, Barbara L.

    2010-01-01

    Premature delivery is the leading cause of infant mortality in the United States. Currently, premature delivery cannot be prevented and new treatments are difficult to develop due to the inability to diagnose symptoms prior to uterine contractions. Cervical ripening is a long period that precedes the active phase of uterine contractions and cervical dilation. The changes in the microstructure of the cervix during cervical ripening suggest that the ultrasonic attenuation should decrease. The objective of this study is to use the reference phantom algorithm to estimate the ultrasonic attenuation in the cervix of pregnant human patients. Prior to applying the algorithm to in vivo human data, two homogeneous phantoms with known attenuation coefficients were used to validate the algorithm and to find the length and the width of the region of interest (ROI) that achieves the smallest error in the attenuation coefficient estimates. In the phantom data, we found that the errors in the attenuation coefficients estimates are less than 12% for ROIs that contain 40 wavelengths or more axially and 30 echo lines or more laterally. The reference phantom algorithm was then used to obtain attenuation maps of the echoes from two human pregnant cervices at different gestational ages. It was observed that the mean of the attenuation coefficient estimates in the cervix of the patient at a more advanced gestational age is smaller than the mean of the attenuation coefficient estimates in the cervix of the patient at an earlier gestational age which suggests that ultrasonic attenuation decreases with increasing gestational age. We also observed a large variance between the attenuation coefficient estimates in the different regions of the cervix due to the natural variation in tissue microstructures across the cervix. The preliminary results indicate that the algorithm could potentially provide an important diagnostic tool for diagnosing the risk of premature delivery. PMID:20570308

  19. Estimate of the attenuation coefficient using a clinical array transducer for the detection of cervical ripening in human pregnancy.

    PubMed

    Labyed, Yassin; Bigelow, Timothy A; McFarlin, Barbara L

    2011-01-01

    Premature delivery is the leading cause of infant mortality in the United States. Currently, premature delivery cannot be prevented and new treatments are difficult to develop due to the inability to diagnose symptoms prior to uterine contractions. Cervical ripening is a long period that precedes the active phase of uterine contractions and cervical dilation. The changes in the microstructure of the cervix during cervical ripening suggest that the ultrasonic attenuation should decrease. The objective of this study is to use the reference phantom algorithm to estimate the ultrasonic attenuation in the cervix of pregnant human patients. Prior to applying the algorithm to in vivo human data, two homogeneous phantoms with known attenuation coefficients were used to validate the algorithm and to find the length and the width of the region of interest (ROI) that achieves the smallest error in the attenuation coefficient estimates. In the phantom data, we found that the errors in the attenuation coefficients estimates are less than 12% for ROIs that contain 40 wavelengths or more axially and 30 echo lines or more laterally. The reference phantom algorithm was then used to obtain attenuation maps of the echoes from two human pregnant cervices at different gestational ages. It was observed that the mean of the attenuation coefficient estimates in the cervix of the patient at a more advanced gestational age is smaller than the mean of the attenuation coefficient estimates in the cervix of the patient at an earlier gestational age which suggests that ultrasonic attenuation decreases with increasing gestational age. We also observed a large variance between the attenuation coefficient estimates in the different regions of the cervix due to the natural variation in tissue micro-structures across the cervix. The preliminary results indicate that the algorithm could potentially provide an important diagnostic tool for diagnosing the risk of premature delivery. Copyright © 2010

  20. FLUXNET2015 Dataset: Batteries included

    NASA Astrophysics Data System (ADS)

    Pastorello, G.; Papale, D.; Agarwal, D.; Trotta, C.; Chu, H.; Canfora, E.; Torn, M. S.; Baldocchi, D. D.

    2016-12-01

    The synthesis datasets have become one of the signature products of the FLUXNET global network. They are composed from contributions of individual site teams to regional networks, being then compiled into uniform data products - now used in a wide variety of research efforts: from plant-scale microbiology to global-scale climate change. The FLUXNET Marconi Dataset in 2000 was the first in the series, followed by the FLUXNET LaThuile Dataset in 2007, with significant additions of data products and coverage, solidifying the adoption of the datasets as a research tool. The FLUXNET2015 Dataset counts with another round of substantial improvements, including extended quality control processes and checks, use of downscaled reanalysis data for filling long gaps in micrometeorological variables, multiple methods for USTAR threshold estimation and flux partitioning, and uncertainty estimates - all of which accompanied by auxiliary flags. This "batteries included" approach provides a lot of information for someone who wants to explore the data (and the processing methods) in detail. This inevitably leads to a large number of data variables. Although dealing with all these variables might seem overwhelming at first, especially to someone looking at eddy covariance data for the first time, there is method to our madness. In this work we describe the data products and variables that are part of the FLUXNET2015 Dataset, and the rationale behind the organization of the dataset, covering the simplified version (labeled SUBSET), the complete version (labeled FULLSET), and the auxiliary products in the dataset.

  1. Estimation of Transmitting Power to Compensate for Rain Attenuation for a Broadcasting Satellite System in the 21-GHz Band

    NASA Astrophysics Data System (ADS)

    Minematsu, Fumiaki; Tanaka, Shoji; Nakagawa, Hitoshi; Kawaguchi, Yutaka

    2002-01-01

    1. INTRODUCTION Rain attenuation in the 21-GHz band is much larger than that in the conventionally used 12-GHz band and the rain attenuation causes more serious program interruptions compared with that in the 12-GHz band. We are now studying an advanced broadcasting satellite in the 21-GHz band that enables adaptive compensation for heavy rain area by boosted beams using an on-board phased-array-transmitting antenna. To know the scale of this satellite system, it is important to estimate transmitting power needed to compensate for rain attenuation. Rain attenuation has so close association with rainfall that it is possible to estimate rain attenuation by measured rainfall. Japan meteorological agency is measuring 1-hour rainfalls for about 1300 locations in Japan. In this study, 1-hour rainfall data accumulated at more than 1000 locations over a period of 20 years were used statistically to grasp rainfall distribution throughout Japan and the transmitting power for compensation was estimated by use of these data. 2. CALCULATION MODEL FOR TRANSMITTING POWER ESTIMATION Assumed rain attenuation compensation area for Japanese archipelago was divided into 112 square areas. A size of each square was 0.1 degree in terms of azimuth and elevation angle for the beam direction of satellite transmitting antenna. For calculation, the link margin of 3.5 dB for clear sky was given to the area where 1-hour rainfall not larger than 3 mm was detected. For other square areas where 1-hour rainfall larger than 3 mm was detected, the link margin of 12 dB was given. The former link margin corresponds to the service availability of 99 % and the latter does to that of 99.9 % in an average year in Tokyo. A total system efficiency included radiation efficiency of the transmitting antenna of 1.0 was assumed. As modulation scheme, trellis coded 8-PSK (TC8PSK) was assumed. The required reception CN ratio for TC8PSK is 10.7 dB. As to TC8PSK, the baud rate of 57.72 Mbaud gives more than 100 Mbps

  2. Engineering biodegradable polyester elastomers with antioxidant properties to attenuate oxidative stress in tissues

    PubMed Central

    van Lith, R.; Gregory, E.K.; Yang, J.; Kibbe, M.R.; Ameer, G.A.

    2014-01-01

    Oxidative stress plays an important role in the limited biological compatibility of many biomaterials due to inflammation, as well as in various pathologies including atherosclerosis and restenosis as a result of vascular interventions. Engineering antioxidant properties into a material is therefore a potential avenue to improve the biocompatibility of materials, as well as to locally attenuate oxidative stress-related pathologies. Moreover, biodegradable polymers that have antioxidant properties built into their backbone structure have high relative antioxidant content and may provide prolonged, continuous attenuation of oxidative stress while the polymer or its degradation products are present. In this report, we describe the synthesis of poly(1,8-octanediol-co-citrate-co-ascorbate) (POCA), a citric-acid based biodegradable elastomer with native, intrinsic antioxidant properties. The in vitro antioxidant activity of POCA as well as its effects on vascular cells in vitro and in vivo were studied. Antioxidant properties investigated included scavenging of free radicals, iron chelation and the inhibition of lipid peroxidation. POCA reduced reactive oxygen species generation in cells after an oxidative challenge and protected cells from oxidative stress-induced cell death. Importantly, POCA antioxidant properties remained present upon degradation. Vascular cells cultured on POCA showed high viability, and POCA selectively inhibited smooth muscle cell proliferation, while supporting endothelial cell proliferation. Finally, preliminary data on POCA-coated ePTFE grafts showed reduced intimal hyperplasia when compared to standard ePTFE grafts. This biodegradable, intrinsically antioxidant polymer may be useful for tissue engineering application where oxidative stress is a concern. PMID:24976244

  3. Engineering biodegradable polyester elastomers with antioxidant properties to attenuate oxidative stress in tissues.

    PubMed

    van Lith, Robert; Gregory, Elaine K; Yang, Jian; Kibbe, Melina R; Ameer, Guillermo A

    2014-09-01

    Oxidative stress plays an important role in the limited biological compatibility of many biomaterials due to inflammation, as well as in various pathologies including atherosclerosis and restenosis as a result of vascular interventions. Engineering antioxidant properties into a material is therefore a potential avenue to improve the biocompatibility of materials, as well as to locally attenuate oxidative stress-related pathologies. Moreover, biodegradable polymers that have antioxidant properties built into their backbone structure have high relative antioxidant content and may provide prolonged, continuous attenuation of oxidative stress while the polymer or its degradation products are present. In this report, we describe the synthesis of poly(1,8-octanediol-co-citrate-co-ascorbate) (POCA), a citric-acid based biodegradable elastomer with native, intrinsic antioxidant properties. The in vitro antioxidant activity of POCA as well as its effects on vascular cells in vitro and in vivo were studied. Antioxidant properties investigated included scavenging of free radicals, iron chelation and the inhibition of lipid peroxidation. POCA reduced reactive oxygen species generation in cells after an oxidative challenge and protected cells from oxidative stress-induced cell death. Importantly, POCA antioxidant properties remained present upon degradation. Vascular cells cultured on POCA showed high viability, and POCA selectively inhibited smooth muscle cell proliferation, while supporting endothelial cell proliferation. Finally, preliminary data on POCA-coated ePTFE grafts showed reduced intimal hyperplasia when compared to standard ePTFE grafts. This biodegradable, intrinsically antioxidant polymer may be useful for tissue engineering application where oxidative stress is a concern.

  4. Updated data on effective and safe immunizations with live-attenuated vaccines for children after living donor liver transplantation.

    PubMed

    Shinjoh, Masayoshi; Hoshino, Ken; Takahashi, Takao; Nakayama, Tetsuo

    2015-01-29

    Although immunizations using live-attenuated vaccines are not recommended for children post-liver transplant due to their theoretical risks, they will inevitably encounter vaccine-preventable viral diseases upon returning to real-life situations. The window of opportunity for vaccination is usually limited prior to transplantation because these children often have unstable disease courses. Also, vaccine immunity does not always persist after transplantation. Beginning in 2002, subcutaneous immunizations with four individual live-attenuated vaccines (measles, rubella, varicella, and mumps) to pediatric patients following living donor liver transplantation (LDLT) were performed for those who fulfilled the clinical criteria, including humoral and cell-mediated immunity. Written informed consent was collected. We included the study on 70 immunizations for 18 cases that we reported in 2008 (Shinjoh et al., 2008). A total of 196 immunizations were administered to 48 pediatric post-LDLT recipients. Of these, 144 were first immunizations and 52 were repeated immunizations following LDLT. The seroconversion rates at the first dose for measles (AIK-C), rubella (TO-336), varicella (Oka), and mumps (Hoshino) were 100% (36/36), 100% (35/35), 70% (23/33), and 75% (24/32), respectively. Antibody levels did not fall over time in patients immunized with rubella vaccine. Three mild cases of breakthrough varicella were observed. Two cases with transient parotid gland swelling were observed after mumps immunization. Two admissions because of fever at 2-3 weeks after the measles vaccine were reported but the patients had no symptoms of measles. Immunizations using selected live-attenuated vaccines were safe and effective for post-LDLT children who were not severely immunosuppressed. However, with the exception of rubella, repeated immunization may be necessary. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Regional Phase Attenuation across the Turkish-Iranian Plateau

    NASA Astrophysics Data System (ADS)

    Sandvol, E. A.; Kaviani, A.; Ku, W.; Ghalib, H. A. A.; Burch, K.

    2015-12-01

    We have constructed and validated regional wave (Pg and Lg) attenuation models for the crust and upper mantle throughout the Iranian plateau and surrounding regions. This research has increased ray path coverage of critical areas and help to create robust regional phase amplitude and attenuation models. We have recently combined our Iranian data set with our existing Middle Eastern Lg waveform database including stations from the recent CDCAT seismic experiment in central Anatolia. Together, these two data sets give us reasonably good coverage of the northern Middle East using both a two-station and reverse-two-station (RTM) attenuation measurements. We have also processed Pg waveforms in order to obtain robust estimates of Qp in the crust within the Anatolian-Iranian plateau. In general we have found a good correlation between Lg and Pg Q values with the exception of northwestern Iran. We are using our models of Qp and Qs for the crust to better understand the origin of the crustal models and to help determine the origin of the seismic anomalies in the crust beneath the Turkish-Iranian Plateau. We will correlate our Q models with variations in seismic wave speed from ambient noise tomography and local body wave tomography to understand whether composition or temperature anomalies are generating the observed seismic anomalies.

  6. Prediction of spectral acceleration response ordinates based on PGA attenuation

    USGS Publications Warehouse

    Graizer, V.; Kalkan, E.

    2009-01-01

    Developed herein is a new peak ground acceleration (PGA)-based predictive model for 5% damped pseudospectral acceleration (SA) ordinates of free-field horizontal component of ground motion from shallow-crustal earthquakes. The predictive model of ground motion spectral shape (i.e., normalized spectrum) is generated as a continuous function of few parameters. The proposed model eliminates the classical exhausted matrix of estimator coefficients, and provides significant ease in its implementation. It is structured on the Next Generation Attenuation (NGA) database with a number of additions from recent Californian events including 2003 San Simeon and 2004 Parkfield earthquakes. A unique feature of the model is its new functional form explicitly integrating PGA as a scaling factor. The spectral shape model is parameterized within an approximation function using moment magnitude, closest distance to the fault (fault distance) and VS30 (average shear-wave velocity in the upper 30 m) as independent variables. Mean values of its estimator coefficients were computed by fitting an approximation function to spectral shape of each record using robust nonlinear optimization. Proposed spectral shape model is independent of the PGA attenuation, allowing utilization of various PGA attenuation relations to estimate the response spectrum of earthquake recordings.

  7. Safety of a live attenuated Erysipelothrix rhusiopathiae vaccine for swine.

    PubMed

    Neumann, Eric J; Grinberg, Alex; Bonistalli, Kathryn N; Mack, Hamish J; Lehrbach, Philip R; Gibson, Nicole

    2009-03-30

    Infection with Erysipelothrix rhusiopathiae has a significant economic impact on pig production systems worldwide. Both inactivated and attenuated vaccines are available to prevent development of clinical signs of swine erysipelas. The ability of a live attenuated E. rhusiop