Measuring soil sydric content by the attenuation of a microwave signal

International Nuclear Information System (INIS)

Orden, S.; Goldberg, M.; Landini, A.; Sainato, C.; Bottini, L.; Arrigo, N.

1995-01-01

Measuring soil water content by means of microwave signal attenuation. The attenuation of microwave signal was used to measure the moisture of various soils. Samples of three soils with different textures and organic matter contents were used. The attenuation of the transmitted electromagnetic signal was measured for each sample with different values of soil moisture. Linear regression models were used to fit the experimental values obtained, and the 95% prediction interval was estimated for the attenuation. From the comparison between the moisture values obtained with this method and those of the gravimetric method, the advantages of the first one are seen, both in speed and in the possibility to estimate the in situ moisture, even if this method has a greater relative error. This method would be useful to operate an automatic control irrigation system, preventing hydric stress when the values of soil moisture reach near field capacity. (author) [es

The Self Attenuation Correction for Holdup Measurements, a Historical Perspective

International Nuclear Information System (INIS)

Oberer, R. B.; Gunn, C. A.; Chiang, L. G.

2006-01-01

Self attenuation has historically caused both conceptual as well as measurement problems. The purpose of this paper is to eliminate some of the historical confusion by reviewing the mathematical basis and by comparing several methods of correcting for self attenuation focusing on transmission as a central concept

Optimization of Power Consumption for Centrifugation Process Based on Attenuation Measurements

Science.gov (United States)

Salim, M. S.; Abd Malek, M. F.; Sabri, Naseer; Omar, M. Iqbal bin; Mohamed, Latifah; Juni, K. M.

2013-04-01

The main objective of this research is to produce a mathematical model that allows decreasing the electrical power consumption of centrifugation process based on attenuation measurements. The centrifugation time for desired separation efficiency may be measured to determine the power consumed of laboratory centrifuge device. The power consumption is one of several parameters that affect the system reliability and productivity. Attenuation measurements of wave propagated through blood sample during centrifugation process were used indirectly to measure the power consumption of device. A mathematical model for power consumption was derived and used to modify the speed profile of centrifuge controller. The power consumption model derived based on attenuation measurements has successfully save the power consumption of centrifugation process keeping high separation efficiency. 18kW.h monthly for 100 daily time device operation had been saved using the proposed model.

Optimization of Power Consumption for Centrifugation Process Based on Attenuation Measurements

International Nuclear Information System (INIS)

Salim, M S; Iqbal bin Omar, M; Malek, M F Abd; Mohamed, Latifah; Sabri, Naseer; Juni, K M

2013-01-01

The main objective of this research is to produce a mathematical model that allows decreasing the electrical power consumption of centrifugation process based on attenuation measurements. The centrifugation time for desired separation efficiency may be measured to determine the power consumed of laboratory centrifuge device. The power consumption is one of several parameters that affect the system reliability and productivity. Attenuation measurements of wave propagated through blood sample during centrifugation process were used indirectly to measure the power consumption of device. A mathematical model for power consumption was derived and used to modify the speed profile of centrifuge controller. The power consumption model derived based on attenuation measurements has successfully save the power consumption of centrifugation process keeping high separation efficiency. 18kW.h monthly for 100 daily time device operation had been saved using the proposed model.

Seismic Attenuation of Teleseismic Body Waves in Cascadia, Measured on the Amphibious Array

Science.gov (United States)

Eilon, Z.; Abers, G. A.

2015-12-01

Fundamental questions remain about the nature of the asthenosphere, including its dynamical relationship to overlying lithosphere, melt content, and entrainment in subduction zones. We examine the evolution of this low-velocity, highly attenuating layer using data from the Cascadia Initiative's Amphibious Array, which provides unprecedented coverage of an oceanic plate from ridge crest to trench to sub-arc. Our study extends the suite of measurements achievable with OBS data, augmenting traditional travel time analysis with integrated attenuation data that are a powerful tool for imaging melt/fluids and the variation of asthenospheric character with age. Cooling models, coupled with experimentally-derived anelastic scaling relationships, indicate that thermal gradients should cause appreciable decrease in attenuation of teleseismic body waves with increasing age. This long-wavelength cooling trend may be perturbed by highly attenuating melt or volatiles concentrated at the ridge axis or beneath the Cascades arc, depending on melt fraction and pore geometry. Attenuation beyond the trench should be a strong function of the fate of asthenospheric entrainment beneath subducted plates, with implications for mass transfer to the deep mantle as well as recent models of sub-slab anisotropy. The Amphibious Array, with 6.0 teleseismic earthquakes. We use a spectral ratio method to compute differential attenuation (Δt*) from body wave teleseisms recorded at OBS and land stations, allowing us to estimate path-integrated quality factor in the upper mantle. Preliminary results reveal variations of ~3 s in differential travel time and >0.5 s in ΔtS* across the 0-10 Ma oceanic plate, demonstrating the strong thermal control on anelasticity. Large values of Δt* observed east of the trench may indicate entrainment of highly attenuating asthenosphere during subduction, although more work is required to categorize and remove the signal of the overriding plate. This work complements

Attenuation measurements of ultrasound in a kaolin-water slurry. A linear dependence upon frequency

International Nuclear Information System (INIS)

Greenwood, M.S.; Mai, J.L.; Good, M.S.

1993-01-01

The attenuation of ultrasound through a kaolin-water slurry was measured for frequencies ranging from 0.5 to 3.0 MHz. The maximum concentration of the slurry was for a weight percentage of 44% (or a volume fraction of 0.24). The goal of these measurements was to assess the feasibility of using ultrasonic attenuation to determine the concentration of a slurry of known composition. The measurements were obtained by consecutively adding kaolin to the slurry and measuring the attenuation at each concentration. After reaching a maximum concentration a dilution technique was used, in which an amount of slurry was removed and water was added, to obtain the attenuation as a function of the concentration. The dilution technique was the more effective method to obtain calibration data. These measurements were carried out using two transducers, having a center frequency of 2.25 MHz, separated by 0.1016m (4.0 in.). The maximum attenuation measured in these experiments was about 100Np/m, but the experimental apparatus has the capability of measuring a larger attenuation if the distance between the two transducers is decreased. For a given frequency, the data show that ln V/V 0 depends linearly upon the volume fraction (V is the received voltage for the slurry and V 0 is that obtained for water). This indicated that each particle acts independently in attenuating ultrasound. 12 refs., 7 figs., 3 tabs

Measurement Method of Temporal Attenuation by Human Body in Off-the-Shelf 60 GHz WLAN with HMM-Based Transmission State Estimation

Directory of Open Access Journals (Sweden)

Yusuke Koda

2018-01-01

Full Text Available This paper discusses a measurement method of time-variant attenuation of IEEE 802.11ad wireless LAN signals in the 60 GHz band induced by human blockage. The IEEE 802.11ad access point (AP transmits frames intermittently, not continuously. Thus, to obtain the time-varying signal attenuation, it is required to estimate the duration in which the AP transmitted signals. To estimate whether the AP transmitted signals or not at each sampling point, this paper applies a simple two-state hidden Markov model. In addition, the validity of the model is tested based on Bayesian information criterion in order to prevent model overfitting and consequent invalid results. The measurement method is validated in that the distribution of the time duration in which the signal attenuates by 5 dB is consistent with the existing statistical model and the range of the measured time duration in which the signal attenuation decreases from 5 dB to 0 dB is similar to that in the previous report.

Measured anisotropic air flow resistivity and sound attenuation of glass wool

DEFF Research Database (Denmark)

Tarnow, Viggo

2002-01-01

Department of Mechanical Engineering, Technical University of Denmark, Bygning 358, DK 2800 Lyngby, Denmark The air flow resistivity of glass wool has been measured in different directions. The glass wool was delivered from the manufacturer as slabs measuring 100×600×900 mm3, where the surface 600...... 7.75 kPa s m**2. A formula for prediction of resistivity for other densities is given. By comparing measured values of sound attenuation with results calculated from resistivity data, it is demonstrated that the measured attenuation can be predicted in a simple manner. ©2002 Acoustical Society...

Attenuation Modified by DIG and Dust as Seen in M31

Energy Technology Data Exchange (ETDEWEB)

Tomičić, Neven; Kreckel, Kathryn; Schinnerer, Eva [Max Planck Institute for Astronomy (MPIA), Königstuhl 17, 69117 Heidelberg (Germany); Groves, Brent [School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia); Sandstrom, Karin [Center for Astrophysics and Space Sciences, Department of Physics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093 (United States); Kapala, Maria [Department of Astronomy, University of Cape Town, Republic of South Africa (South Africa); Blanc, Guillermo A. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Leroy, Adam, E-mail: tomicic@mpia-hd.mpg.de [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)

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.

Continental Fog Attenuation Empirical Relationship from Measured Visibility Data

Directory of Open Access Journals (Sweden)

F. Nadeem

2010-12-01

Full Text Available Free Space Optics (FSO has the great potential for future communication applications. However, weather influenced reduced availability had been the main cause for its restricted growth. Among different weather influences fog plays the major role. A new model generalized for all FSO wavelengths, has been proposed for the prediction of continental fog attenuation using visibility data. The performance of the proposed model has been compared with well known models for measured attenuation data of Continental fog. The comparison has been performed in terms of Root Mean Square Error (RMSE.

Measurement of attenuation cross-sections of some fatty acids in the ...

Indian Academy of Sciences (India)

These quantities were obtained by utilizing experimentally measured values of mass attenuation coefficients ( μ m ) . A NaI(Tl) scintillation detector with 8.2% (at 662 keV) resolution was used for detecting of attenuated γ -photons. The variation in Zeff and Neff of fatty acids with energy is discussed. The experimental and ...

Determination of H, C, N, O content of bulk materials from neutron-attenuation measurements

International Nuclear Information System (INIS)

Overley, J.C.

1985-01-01

Several bulk samples ranging from chemical compounds to cereal grains have been nondestructively analyzed through neutron-attenuation measurements. A fast-neutron continuum was produced by an accelerator. Attenuations were measured by pulsed-beam, time-of-flight techniques. Average hydrogen, carbon, nitrogen, and oxygen contents were deduced by comparing attenuations to those measured for pure elements. Statistical precisions of 0.3-0.7 atomic percent were achieved for each element in about 10 min. Comparisons with results of other analysis techniques indicate that similar levels of accuracy are possible, even in the presence of small amounts of heavier elements. (author)

Rain attenuation studies from radiometric and rain DSD measurements at two tropical locations

Science.gov (United States)

Halder, Tuhina; Adhikari, Arpita; Maitra, Animesh

2018-05-01

Efficient use of satellite communication in tropical regions demands proper characterization of rain attenuation, particularly, in view of the available popular propagation models which are mostly based on temperate climatic data. Thus rain attenuations at frequencies 22.234, 23.834 and 31.4/30 GHz over two tropical locations Kolkata (22.57°N, 88.36°E, India) and Belem (1.45°S, 48.49° W, Brazil), have been estimated for the year 2010 and 2011, respectively. The estimation has been done utilizing ground-based disdrometer observations and radiometric measurements over Earth-space path. The results show that rain attenuation estimations from radiometric data are reliable only at low rain rates (measurements show good agreement with the ITU-R model, even at high rain rates (upto100 mm/h). Despite having significant variability in terms of drop size distribution (DSD), the attenuation values calculated from DSD data (disdrometer measurements) at Kolkata and Belem differ a little for the rain rates below 30 mm/h. However, the attenuation values, obtained from radiometric measurements at the two places, show significant deviations ranging from 0.54 dB to 3.2 dB up to a rain rate of 30 mm/h, on account of different rain heights, mean atmospheric temperatures and climatology of the two locations.

Measurement of atomic number and mass attenuation coefficient in ...

Indian Academy of Sciences (India)

literature on the measurement of mass attenuation coefficient in magnesium ferrite. The knowledge of photon ... pure) MgO and Fe2O3. The details of experimental ... and (4 4 0) planes belonging to cubic spinel structure. The XRD pattern ...

Scintigraphic measurements of gastric emptying corrected for differences in tissue attenuation

Energy Technology Data Exchange (ETDEWEB)

Lauritzen, J.B.; Hoejgaard, L.; Uhrenholdt, A. (Copenhagen Univ. (Denmark). Hvidovre Hospital)

1983-10-01

In order to evaluate the importance of variations in tissue attenuation in scintigraphic measurements of gastric emptying, both in vivo and in vitro measurements of count rates from an encapsulated sup(99m)Tc dose were performed in different parts of the stomach. The obtained individual tissue correction factors were applied in the calculation of gastric emptying rates by gamma camera in healthy volunteers. The results showed that the anterior gamma camera scan without correction for differences in tissue attenuation underestimated the gastric emptying rate by 11% if the results were expressed as percentage meal emptied over 60 minutes.

Relationship between comfort and attenuation measurements for two types of earplugs

Directory of Open Access Journals (Sweden)

David C Byrne

2011-01-01

Full Text Available Noise-induced hearing loss is almost always preventable if properly fitted hearing protectors are worn to reduce exposure. Many individuals choose not to wear hearing protection because it may interfere with effective communication in the workplace or it may be uncomfortable. Hearing protector comfort has not received the same amount of attention as noise reduction capability. The present study was conducted to evaluate the comfort level of two different types of insert earplugs as well as the attenuation levels achieved by the earplugs. Attenuation levels were obtained with a commercially available earplug fit-test system, and the comfort ratings were obtained by questionnaire. The primary research objective was to determine whether hearing protector comfort was related to measured attenuation values. A linear mixed effects model provided evidence for an inverse relationship between comfort and attenuation.

Measurements of the ultrasonic attenuation and velocity variation in neutron irradiated quartz for an intermediate dose of 2.6x1019 n/cm2

International Nuclear Information System (INIS)

Keppens, V.; Laermans, C.

1992-01-01

Ultrasonic measurements in neutron-irradiated quartz are carried out for an intermediate dose of 2.6x10 19 n/cm 2 . The variation of the velocity of sound has been measured and previous attenuation measurements are extended to temperatures below 1.2 K. The TS-parameters anti P and γ 1 are calculated from numerical fittings to the tunneling model. The obtained values continue the tendency of previous measurements for lower neutron doses, where a linear increase of anti P with the dose was found. This behaviour, however, is not followed by a higher dose, situated near the ''threshold regime''. (orig.)

Analysis of optical attenuation from measured visibility data in islamabad, pakistan

International Nuclear Information System (INIS)

Khan, R.; Khan, M.S.

2018-01-01

FSOL (Free-Space Optical Links) are becoming very popular due to the inherent advantages of high data rates, rapid deployment, portability, cost effective and immunity to electromagnetic interference. FSOL is a line-of-sight technology that uses a modulated beam of light to transmit and receive the data of multiple of Giga Bit per second. FSOL uses the free space or atmosphere as a communication channel. Optical signal launched at transmitter end, travels through the atmosphere and reaches to the receiver, is severely affected by the local atmospheric conditions. Atmosphere contains different atmospheric particulates like fog, rain, snow, smog, clouds and haze. These atmospheric particulates, particularly fog, effect the propagation of optical signal passing through the atmosphere and cause significant amount of optical attenuation. In order to deploy FSO system, a detailed analysis of local weather condition is much more important. Here, we present the measured visibility data for analysis of optical attenuation. Visibility data was measured at COMSATS Institute of Information Technology from 2009-2012. Percentage CDF (Cumulative Distribution Function) is used to find out the detailed insight about the optical attenuation of FSOL. Yearly based CDFs is compared with each other which clearly suggest that almost 99% of time optical attenuation remains within the range of 2 dB/km. (author)

Ultrasonic attenuation measurements and 'glassy' behaviour of neutron irradiated quartz

International Nuclear Information System (INIS)

Laermans, C.; Esteves, V.; Vanelstraete, A.

1986-01-01

The ultrasonic attenuation of longitudinal acoustic waves in slightly disordered crystalline quartz has been measured over a temperature range from 1.3 to 300 K, using the pulse-echo technique. Neutron irradiation is demonstrated to increase the ultrasonic attenuation at low temperatures indicating the presence of two-level tunneling systems similar to those of glasses. The present low-temperature acoustic results agree with a frequency independence and a T 3 behaviour for the relaxation process predicted by the two-level tunneling TLS-model where the regime ωT 1 >> 1 holds. (author)

Measurements of linear attenuation coefficients of irregular shaped samples by two media method

International Nuclear Information System (INIS)

Singh, Sukhpal; Kumar, Ashok; Thind, Kulwant Singh; Mudahar, Gurmel S.

2008-01-01

The linear attenuation coefficient values of regular and irregular shaped flyash materials have been measured without knowing the thickness of a sample using a new technique namely 'two media method'. These values have also been measured with a standard gamma ray transmission method and obtained theoretically with winXCOM computer code. From the comparison it is reported that the two media method has given accurate results of attenuation coefficients of flyash materials

Precision and accuracy in CT attenuation measurement of vascular wall using region-of-interest supported by differentiation curve

International Nuclear Information System (INIS)

Suzuki, Shigeru; Kidouchi, Takashi; Kuwahara, Sadatoshi; Vembar, Mani; Takei, Ryoji; Yamamoto, Asako

2012-01-01

Objectives: To evaluate the precision and accuracy in CT attenuation measurement of vascular wall using region-of-interest (ROI) supported by differentiation curves. Study design: We used vascular models (actual attenuation value of the wall: 87 HU) with wall thicknesses of 1.5, 1.0, or 0.5 mm, filled with contrast material of 250, 348, or 436 HU. The nine vascular models were scanned with a 64-detector CT. The wall attenuation values were measured using three sizes (diameter: 0.5, 1.0, and 1.5 mm) of ROIs without differentiation curves. Sixteen measurements were repeated for each vascular model by each of two operators. Measurements supported by differentiation curves were also performed. We used analyses of variance with repeated measures for the measured attenuations for each size of the ROI. Results: Without differentiation curves, there were significant differences in the attenuation values of the wall among the three densities of contrast material, and the attenuation values tended to be overestimated more as the contrast material density increased. Operator dependencies were also found in measurements for 0.5- and 1.5-mm thickness models. With differentiation curves, measurements were not possible for 0.5- and 1.0-mm thickness models. Using differentiation curves for 1.5-mm thickness models with a ROI of 1.0- or 1.5-mm diameter, the wall attenuations were not affected by the contrast material densities and were operator independent, measuring between 75 and 103 HU. Conclusions: The use of differentiation curves can improve the precision and accuracy in wall attenuation measurement using a ROI technique, while measurements for walls of ≤1.0 mm thickness are difficult.

Calculations and measurements of β-ray attenuation for determining density in an inhomogenous medium

International Nuclear Information System (INIS)

Williamson, T.G.; Mackinnon, J.G.; Frisch, A.F.; Jenkins, R.W. Jr.

1980-01-01

A model for the distribution of tobacco strands in a cigarette is proposed to explain the discrepancy between density as measured by weight and volume and that as measured by β-ray attenuation and to explain the large deviation of the β-ray measurements from the mean value. The parameters which contribute to this uncertainty are slope of the β-ray attenuation curve, the mean path length through the mass element, and the material volume fraction. (author)

Symphony orchestra musicians′ use of hearing protection and attenuation of custom-made hearing protectors as measured with two different real-ear attenuation at threshold methods

Directory of Open Access Journals (Sweden)

K H Huttunen

2011-01-01

Full Text Available Despite a high level of sound exposure and a fairly large selection of earplugs available, musicians have often been reported to use personal hearing protectors only seldom. For better hearing conservation, it is important to identify and eliminate the causes for the low motivation to use hearing protection. We explored the usage rate of custom-molded musician′s earplugs (ER-15 among 15 symphony orchestra musicians with a questionnaire, and measured the attenuation properties of their earplugs with a Real-Ear Attenuation at Threshold (REAT procedure in a sound field. Earplug use was found to be low, and the musicians reported that earplugs hampered listening to their own and their colleagues′ playing; earplugs affected either timbre or dynamics, or both. Additionally, several reasons related to discomfort of use were itemized, but the musicians who consistently used their earplugs did so in spite of problems with use. The REAT values obtained in sound field were relatively close to the manufacturer′s nominal specifications, being 13.7 dB, on average. In the frequency range studied (0.125-8 kHz, individual variation in REAT was, however, up to 15 dB across the measured frequencies. Fluctuation in attenuation might be related to low use of hearing protectors, and REAT measured at fixed center frequencies may be too robust a method to uncover it. We therefore tested 10 additional subjects to find out whether a sweeping signal used in Bιkιsy audiometry would bring more detailed information on earplug attenuation. Mean attenuation was found to be somewhat closer to the nominal attenuation of the ER-9 and ER-15 earplugs up to about 1 kHz, whereas REAT measurements in sound field revealed more even attenuation at frequencies between 1 and 6 kHz. No significant association was found between earplug attenuation properties and earplug use. It was concluded that support and determination to get accustomed to hearing protector use are important

Statistical modeling of optical attenuation measurements in continental fog conditions

Science.gov (United States)

Khan, Muhammad Saeed; Amin, Muhammad; Awan, Muhammad Saleem; Minhas, Abid Ali; Saleem, Jawad; Khan, Rahimdad

2017-03-01

Free-space optics is an innovative technology that uses atmosphere as a propagation medium to provide higher data rates. These links are heavily affected by atmospheric channel mainly because of fog and clouds that act to scatter and even block the modulated beam of light from reaching the receiver end, hence imposing severe attenuation. A comprehensive statistical study of the fog effects and deep physical understanding of the fog phenomena are very important for suggesting improvements (reliability and efficiency) in such communication systems. In this regard, 6-months real-time measured fog attenuation data are considered and statistically investigated. A detailed statistical analysis related to each fog event for that period is presented; the best probability density functions are selected on the basis of Akaike information criterion, while the estimates of unknown parameters are computed by maximum likelihood estimation technique. The results show that most fog attenuation events follow normal mixture distribution and some follow the Weibull distribution.

Temperature Measurements of the Low-Attenuation Radiographic Ice Ball During CT-Guided Renal Cryoablation

International Nuclear Information System (INIS)

Permpongkosol, Sompol; Link, Richard E.; Kavoussi, Louis R.; Solomon, Stephen B.

2008-01-01

During renal cryoablation a low-attenuation area on CT develops around the cryoprobe. Knowledge of the temperature of the growing low-attenuation area can guide therapy and ensure lethal temperatures. Herein, we report thermocouple results and correlating CT images during the development of the low-attenuation 'radiographic ice ball.' Five patients who underwent percutaneous CT-guided renal cryoablation were identified who had thermocouples inserted and serial intraprocedural CT images that included images with thermocouple measurements of 0 o and sub-0 o C. Thermocouples had been percutaneously placed just beyond the edge of the tumors either to ensure adequate cooling or to ensure safety to adjacent critical structures. Renal cryotherapy under CT guidance produced a growing low-attenuation area corresponding to the radiographic ice ball. When the thermocouple measured 0 o C, CT images showed the thermocouple tip at the edge of the low-attenuation ice ball. At lower temperatures the tip was within the low-attenuation ice ball. We conclude that knowledge of the temperature at the ice ball edge during cryoablation can be used to predict the extent of tissue necrosis and thus provide an estimate of cryotherapy effectiveness during the procedure. Further work is necessary to establish a firm relationship between the thermal conditions and the zone of damage

An apparatus to measure water optical attenuation length for LHAASO-MD

Science.gov (United States)

Li, Cong; Xiao, Gang; Feng, Shaohui; Wang, Lingyu; Li, Xiurong; Zuo, Xiong; Cheng, Ning; Wang, Hui; Gao, Bo; Duan, Zhihao; Liu, Jia; He, Huihai; Saeed, Mohsin; Lhaaso Collaboration

2018-06-01

The large high altitude air shower observatory (LHAASO) is being constructed at 4400 m a.s.l. in Daocheng, Sichuan Province, aiming to reveal the secrets of cosmic rays origin. And it has the largest surface muon detector array in the world. Due to the needs of calibration and construction of muon detector, we developed a water optical attenuation measurement device using an 8 m long water tank. The results are presented for filtered water at wavelength of 405 nm, which proves this apparatus can reach an accuracy of about 20% at 100 m. This apparatus has not only a high precision measurement of water attenuation length up to 100 m but is also very convenient to be used, which is crucial for water optical properties study during LHAASO detector construction.

Weighted backprojection implemented with a non-uniform attenuation map for improved SPECT quantitation

International Nuclear Information System (INIS)

Manglos, S.H.; Jaszczak, R.J.; Floyd, C.E.

1988-01-01

A method is developed to improve quantitation in SPECT imaging by using an attenuation compensation method which includes the correct non-uniform attenuation spatial distribution (''map''). The method is based on the technique of weighted back projection, previously developed for uniform attenuation. The method is tested by imaging a non-uniform phantom, reconstructing with the known attenuation map, and quantitatively comparing the resultant image with the known activity distribution. Reconstructed image profiles are dramatically improved in comparison to reconstructions without compensation or with an assumed uniform attenuation map. Contrast measurements further quantify the improvement. Line spread function distortions seen previously in non-uniform geometries are essentially eliminated by the method. Therefore, the method appears to be appropriate for these geometries, if the non-uniform map can be determined. Some additional image distortions introduced by the compensation method are noted and will require further study

Effect of duct shape, Mach number, and lining construction on measured suppressor attenuation and comparison with theory

Science.gov (United States)

Olsen, W. A.; Krejsa, E. A.; Coats, J. W.

1972-01-01

Noise attenuation was measured for several types of cylindrical suppressors that use a duct lining composed of honeycomb cells covered with a perforated plate. The experimental technique used gave attenuation data that were repeatable and free of noise floors and other sources of error. The suppressor length, the effective acoustic diameter, suppressor shape and flow velocity were varied. The agreement among the attenuation data and two widely used analytical models was generally satisfactory. Changes were also made in the construction of the acoustic lining to measure their effect on attenuation. One of these produced a very broadband muffler.

Filter Paper: Solution to High Self-Attenuation Corrections in HEPA Filter Measurements

International Nuclear Information System (INIS)

Oberer, R.B.; Harold, N.B.; Gunn, C.A.; Brummett, M.; Chaing, L.G.

2005-01-01

An 8 by 8 by 6 inch High Efficiency Particulate Air (HEPA) filter was measured as part of a uranium holdup survey in June of 2005 as it has been routinely measured every two months since 1998. Although the survey relies on gross gamma count measurements, this was one of a few measurements that had been converted to a quantitative measurement in 1998. The measurement was analyzed using the traditional Generalized Geometry Holdup (GGH) approach, using HMS3 software, with an area calibration and self-attenuation corrected with an empirical correction factor of 1.06. A result of 172 grams of 235 U was reported. The actual quantity of 235 U in the filter was approximately 1700g. Because of this unusually large discrepancy, the measurement of HEPA filters will be discussed. Various techniques for measuring HEPA filters will be described using the measurement of a 24 by 24 by 12 inch HEPA filter as an example. A new method to correct for self attenuation will be proposed for this measurement Following the discussion of the 24 by 24 by 12 inch HEPA filter, the measurement of the 8 by 8 by 6 inch will be discussed in detail

The role of aortic wall CT attenuation measurements for the diagnosis of acute aortic syndromes

Energy Technology Data Exchange (ETDEWEB)

Knollmann, Friedrich D., E-mail: friedrich.knollmann@ucdmc.ucdavis.edu [Department of Radiology, University of California, Davis, 4860 Y Street, Sacramento, CA 95817 (United States); Departments of Radiology and Cardiothoracic Surgery, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213 (United States); Lacomis, Joan M.; Ocak, Iclal; Gleason, Thomas [Department of Radiology, University of California, Davis, 4860 Y Street, Sacramento, CA 95817 (United States); Departments of Radiology and Cardiothoracic Surgery, University of Pittsburgh, 200 Lothrop Street, Pittsburgh, PA 15213 (United States)

2013-12-01

Objectives: To determine if measurements of aortic wall attenuation can improve the CT diagnosis of acute aortic syndromes. Methods: CT reports from a ten year period were searched for acute aortic syndromes (AAS). Studies with both an unenhanced and a contrast enhanced (CTA) series that had resulted in the diagnosis of intramural hematoma (IMH) were reviewed. Diagnoses were confirmed by medical records. The attenuation of aortic wall abnormalities was measured. The observed attenuation threshold was validated using studies from 39 new subjects with a variety of aortic conditions. Results: The term “aortic dissection” was identified in 1206, and IMH in 124 patients’ reports. IMH was confirmed in 31 patients, 21 of whom had both unenhanced and contrast enhanced images. All 21 had pathologic CTA findings, and no CTA with IMH was normal. Attenuation of the aortic wall was greater than 45 HUs on the CTA images in all patients with IMH. When this threshold was applied to the new group, sensitivity for diagnosing AAS was 100% (19/19), and specificity 94% (16/17). Addition of unenhanced images did not improve accuracy. Conclusions: Measurements of aortic wall attenuation in CTA have a high negative predictive value for the diagnosis of acute aortic syndromes.

The role of aortic wall CT attenuation measurements for the diagnosis of acute aortic syndromes

International Nuclear Information System (INIS)

Knollmann, Friedrich D.; Lacomis, Joan M.; Ocak, Iclal; Gleason, Thomas

2013-01-01

Objectives: To determine if measurements of aortic wall attenuation can improve the CT diagnosis of acute aortic syndromes. Methods: CT reports from a ten year period were searched for acute aortic syndromes (AAS). Studies with both an unenhanced and a contrast enhanced (CTA) series that had resulted in the diagnosis of intramural hematoma (IMH) were reviewed. Diagnoses were confirmed by medical records. The attenuation of aortic wall abnormalities was measured. The observed attenuation threshold was validated using studies from 39 new subjects with a variety of aortic conditions. Results: The term “aortic dissection” was identified in 1206, and IMH in 124 patients’ reports. IMH was confirmed in 31 patients, 21 of whom had both unenhanced and contrast enhanced images. All 21 had pathologic CTA findings, and no CTA with IMH was normal. Attenuation of the aortic wall was greater than 45 HUs on the CTA images in all patients with IMH. When this threshold was applied to the new group, sensitivity for diagnosing AAS was 100% (19/19), and specificity 94% (16/17). Addition of unenhanced images did not improve accuracy. Conclusions: Measurements of aortic wall attenuation in CTA have a high negative predictive value for the diagnosis of acute aortic syndromes

Comparison of Instantaneous Frequency Scaling from Rain Attenuation and Optical Disdrometer Measurements at K/Q bands

Science.gov (United States)

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

2015-01-01

Rain attenuation is strongly dependent on the rain rate, but also on the rain drop size distribution (DSD). Typically, models utilize an average drop size distribution, such as those developed by Laws and Parsons, or Marshall and Palmer. However, individual rain events may possess drop size distributions which could be significantly different from the average and will impact, for example, fade mitigation techniques which utilize channel performance estimates from a signal at a different frequency. Therefore, a good understanding of the characteristics and variability of the raindrop size distribution is extremely important in predicting rain attenuation and instantaneous frequency scaling parameters on an event-toevent basis. Since June 2014, NASA Glenn Research Center (GRC) and the Politecnico di Milano (POLIMI) have measured the attenuation due to rain in Milan, Italy, on the 20/40 GHz beacon signal broadcast from the Alphasat TDP#5 Aldo Paraboni Q/V-band Payload. Concomitant with these measurements are the measurements of drop size distribution and rain rate utilizing a Thies Clima laser precipitation monitor (disdrometer). In this paper, we discuss the comparison of the predicted rain attenuation at 20 and 40 GHz derived from the drop size distribution data with the measured rain attenuation. The results are compared on statistical and real-time bases. We will investigate the performance of the rain attenuation model, instantaneous frequency scaling, and the distribution of the scaling factor. Further, seasonal rain characteristics will be analysed.

Impact of Scattering Model on Disdrometer Derived Attenuation Scaling

Science.gov (United States)

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.

Snowpack snow water equivalent measurement using the attenuation of cosmic gamma radiation

International Nuclear Information System (INIS)

Osterhuber, R.; Condreva, K.

1998-01-01

Incoming, background cosmic radiation constantly fluxes through the earth's atmosphere. The high energy gamma portion of this radiation penetrates many terrestrial objects, including the winter snowpack. The attenuation of this radiation is exponentially related to the mass of the medium through which it penetrates. For the past three winters, a device measuring cosmic gamma radiation--and its attenuation through snow--has been installed at the Central Sierra Snow Laboratory, near Donner Pass, California. This gamma sensor, measuring energy levels between 5 and 15 MeV, has proved to be an accurate, reliable, non-invasive, non-mechanical instrument with which to measure the total snow water equivalent of a snowpack. This paper analyzes three winters' worth of data and discusses the physics and practical application of the sensor for the collection of snow water equivalent data from a remote location

An in situ measurement of the radio-frequency attenuation in ice at Summit Station, Greenland

OpenAIRE

Avva, J.; Kovac, J. M.; Miki, C.; Saltzberg, D.; Vieregg, A. G.

2014-01-01

We report an in situ measurement of the electric field attenuation length Lα at radio frequencies for the bulk ice at Summit Station, Greenland, made by broadcasting radio-frequency signals vertically through the ice and measuring the relative power in the return ground bounce signal. We find the depth-averaged field attenuation length to be hLαi = 947+92 −85 m at 75 MHz. While this measurement has clear radioglaciological applications, the radio clarity of the ice also has implications for t...

Real-Time Rain Rate Evaluation via Satellite Downlink Signal Attenuation Measurement.

Science.gov (United States)

Giannetti, Filippo; Reggiannini, Ruggero; Moretti, Marco; Adirosi, Elisa; Baldini, Luca; Facheris, Luca; Antonini, Andrea; Melani, Samantha; Bacci, Giacomo; Petrolino, Antonio; Vaccaro, Attilio

2017-08-12

We present the NEFOCAST project (named by the contraction of "Nefele", which is the Italian spelling for the mythological cloud nymph Nephele, and "forecast"), funded by the Tuscany Region, about the feasibility of a system for the detection and monitoring of precipitation fields over the regional territory based on the use of a widespread network of new-generation Eutelsat "SmartLNB" (smart low-noise block converter) domestic terminals. Though primarily intended for interactive satellite services, these devices can also be used as weather sensors, as they have the capability of measuring the rain-induced attenuation incurred by the downlink signal and relaying it on an auxiliary return channel. We illustrate the NEFOCAST system architecture, consisting of the network of ground sensor terminals, the space segment, and the service center, which has the task of processing the information relayed by the terminals for generating rain field maps. We discuss a few methods that allow the conversion of a rain attenuation measurement into an instantaneous rainfall rate. Specifically, we discuss an exponential model relating the specific rain attenuation to the rainfall rate, whose coefficients were obtained from extensive experimental data. The above model permits the inferring of the rainfall rate from the total signal attenuation provided by the SmartLNB and from the link geometry knowledge. Some preliminary results obtained from a SmartLNB installed in Pisa are presented and compared with the output of a conventional tipping bucket rain gauge. It is shown that the NEFOCAST sensor is able to track the fast-varying rainfall rate accurately with no delay, as opposed to a conventional gauge.

Measure of the attenuation curve of a beam of X-rays with TLD-100 dosimeters of LiF

International Nuclear Information System (INIS)

Bonzi, E. V.; Mainardi, R. T.; Germanier, A.; Delgado, V.

2011-10-01

The attenuation curve of a beam of X-rays represents the beam intensity in function of the attenuator thickness interposed between the source and the detector. To know with the major possible precision the attenuation curve is indispensable in procedures of spectral reconstruction. Their periodic measuring also offers valuable information on the correct operation of a tube of X-rays, diagnostic or therapy, when not have a specific detector for that activity. In this work was measured the attenuation curve of a tube of X-rays operated to 50 kV and 0.5 ma, using existent elements in any diagnostic or therapy laboratory with radiations. In the measures commercial aluminum foil was used, bent until 24 times and thermoluminescent dosimeters TLD 100 - LiF. Also, for comparison, was measured this attenuation curve with an ionization chamber brand Capintec model 192. Was determined by X-rays fluorescence the composition of the aluminium foil, since the present elements in the alloy can to affect the form of the attenuation curve. It is interesting to observe that these elements are in very low proportion (ppm) that they do not alter the attenuation capacity of the pure aluminium. Finally in a precision balance we weigh a big piece (30 cm x 100 cm) of aluminium foil and we obtained the thickness in g/c m2. It is possible to obtain attenuation curves of a beam of X-rays, with a high precision procedure and reproducibility. The use of TLD-100 dosimeters of LiF or similar makes that this activity was also quick and simple. (Author)

Experiments on the attenuation of third sound in saturated superfluid helium films

International Nuclear Information System (INIS)

Telschow, K.L.; Galkiewicz, R.K.; Hallock, R.B.

1976-01-01

Upper limits of the attenuation of third sound in saturated superfluid 4 He films have been measured in three separate experiments. Observations at frequencies from 0.1 to 200 Hz indicate that the attenuation in these thick films is substantially lower than would be inferred from the only previous experiment done on saturated films. The third-sound velocity is observed to have the temperature dependence predicted by Bergman

Sparse signal reconstruction from polychromatic X-ray CT measurements via mass attenuation discretization

International Nuclear Information System (INIS)

Gu, Renliang; Dogandžić, Aleksandar

2014-01-01

We propose a method for reconstructing sparse images from polychromatic x-ray computed tomography (ct) measurements via mass attenuation coefficient discretization. The material of the inspected object and the incident spectrum are assumed to be unknown. We rewrite the Lambert-Beer’s law in terms of integral expressions of mass attenuation and discretize the resulting integrals. We then present a penalized constrained least-squares optimization approach for reconstructing the underlying object from log-domain measurements, where an active set approach is employed to estimate incident energy density parameters and the nonnegativity and sparsity of the image density map are imposed using negative-energy and smooth ℓ 1 -norm penalty terms. We propose a two-step scheme for refining the mass attenuation discretization grid by using higher sampling rate over the range with higher photon energy, and eliminating the discretization points that have little effect on accuracy of the forward projection model. This refinement allows us to successfully handle the characteristic lines (Dirac impulses) in the incident energy density spectrum. We compare the proposed method with the standard filtered backprojection, which ignores the polychromatic nature of the measurements and sparsity of the image density map. Numerical simulations using both realistic simulated and real x-ray ct data are presented

Assessment of precipitates of isothermal aged austenitic stainless steel using measurement techniques of ultrasonic attenuation

International Nuclear Information System (INIS)

Kim, Hun Hee; Kim, Hak Joon; Song, Sung Jin; Lim, Byeong Soo; Kim, Kyung Cho

2014-01-01

AISI 316L stainless steel is widely used as a structural material of high temperature thermoelectric power plants, since austenitic stainless steel has excellent mechanical properties. However, creep damage is generated in these components, which are operated under a high temperature and high pressure environment. Several researches have been done on how microstructural changes of precipitates affect to the macroscopic mechanical properties. And they investigate the relation between ultrasonic parameters and metallurgical results. But, these studies are limited by experiment results only. In this paper, attenuations of ultrasonic with isothermal damaged AISI 316L stainless steel were measured. Also, simulation of ultrasonic attenuation with variation of area fraction and size of precipitates were performed. And, from the measured attenuations, metallographic data and simulation results, we investigate the relations between the ultrasonic attenuations and the material properties which is area fraction of precipitates for the isothermal damaged austenitic stainless steel specimens. And, we studied parametric study for investigation of the relation between ultrasonic parameters and metallurgical results of the isothermal damaged AISI 316L stainless steel specimens using numerical methods.

CFHT's SkyProbe: True Atmospheric Attenuation Measurement in the Telescope Field

Science.gov (United States)

Cuillandre, J.-C.; Magnier, E. A.; Isani, S.; Sabin, D.; Knight, W.; Kras, S.; Lai, K.

Developed at the Canada France Hawaii Telescope (CFHT), SkyProbe is a system that allows the direct measurement of the true attenuation by clouds. This measurement is performed approximately once per min, directly on the field viewed by the telescope. It has been possible to make this system relatively inexpensively due to low cost CCD cameras available on the amateur market. A crucial addition to this hardware is the recent availability of a full-sky photometry catalog at the appropriate depth: the Tycho catalog from the Hipparcos mission. A very important element in the SkyProbe data set creation is the automatic data analysis pipeline, Elixir, developed at CFHT for the improved operation of the CFHT wide-field imagers CFH12K and MegaCam. SkyProbe's FITS images are processed in real time, and the pipeline output (a zero point attenuation) provides the current sky transmission to the observers and aids immediate decision making. These measurements are also attached to the archived data, adding a key tool for future use by other astronomers. Specific features of the detector, such as intra pixel quantum efficiency variations, must be taken into consideration since the data are strongly undersampled.

Pulsed x-ray induced attenuation measurements of single mode optical fibers and coupler materials

International Nuclear Information System (INIS)

Johan, A.; Charre, P.

1994-01-01

Pulsed X-ray induced transient radiation attenuation measurements of single mode optical fibers have been performed versus total dose, light wavelength, optical power and fiber coil diameter in order to determine the behavior of parameters sensitive to ionizing radiation. The results did not show any photobleaching phenomenon and the attenuation was found independent of the spool diameter. As expected, transient attenuation was lower for higher wave-lengths. The recovery took place in the millisecond range and was independent of total dose, light wavelength and optical power. In optical modules and devices a large range of behaviors was observed according to coupler material i.e., Corning coupler showed a small peak attenuation that remained more than one day later; on the other hand LiTaO 3 material experienced an order of magnitude higher peak attenuation and a recovery in the millisecond range. For applications with optical fibers and integrated optics devices the authors showed that in many cases the optical fiber (length above 100 m) is the most sensitive device in a transient ionizing radiation field

The development of an experimental set-up for the measurement of acoustic attenuation in sea-water and studies of the usefulness of acoustic attenuation as a parameter in oceanographic research

International Nuclear Information System (INIS)

Barkmann, R.

1982-01-01

A senson element is described for the measurement of ultrasound wave attenuation in water. This device has been developed for in-situ measurements of the additional attenuation caused by particles or air bubbles. Results are presented for the attenuation variations induced by ions and solid-state particles. The method is based on the emission of a 80 μs acoustic sine wave burst at about 10 MHz in a water container of 10 cm length. Then the amplitudes of the decaying echos are registrated, which are caused by reflections at the transducer and the reflector. The sound attenuation coefficient is obtained from the amplitude ratio of the first two echos, taking into account corrections caused by diffraction and reflection effects. (orig./RW) [de

Determination of Dimensionless Attenuation Coefficient in Shaped Resonators

Science.gov (United States)

Daniels, C.; Steinetz, B.; Finkbeiner, J.; Raman, G.; Li, X.

2003-01-01

The value of dimensionless attenuation coefficient is an important factor when numerically predicting high-amplitude acoustic waves in shaped resonators. Both the magnitude of the pressure waveform and the quality factor rely heavily on this dimensionless parameter. Previous authors have stated the values used, but have not completely explained their methods. This work fully describes the methodology used to determine this important parameter. Over a range of frequencies encompassing the fundamental resonance, the pressure waves were experimentally measured at each end of the shaped resonators. At the corresponding dimensionless acceleration, the numerical code modeled the acoustic waveforms generated in the resonator using various dimensionless attenuation coefficients. The dimensionless attenuation coefficient that most closely matched the pressure amplitudes and quality factors of the experimental and numerical results was determined to be the value to be used in subsequent studies.

Measurement of vascular wall attenuation: Comparison of CT angiography using model-based iterative reconstruction with standard filtered back-projection algorithm CT in vitro

International Nuclear Information System (INIS)

Suzuki, Shigeru; Machida, Haruhiko; Tanaka, Isao; Ueno, Eiko

2012-01-01

Objectives: To compare the performance of model-based iterative reconstruction (MBIR) with that of standard filtered back projection (FBP) for measuring vascular wall attenuation. Study design: After subjecting 9 vascular models (actual attenuation value of wall, 89 HU) with wall thickness of 0.5, 1.0, or 1.5 mm that we filled with contrast material of 275, 396, or 542 HU to scanning using 64-detector computed tomography (CT), we reconstructed images using MBIR and FBP (Bone, Detail kernels) and measured wall attenuation at the center of the wall for each model. We performed attenuation measurements for each model and additional supportive measurements by a differentiation curve. We analyzed statistics using analyzes of variance with repeated measures. Results: Using the Bone kernel, standard deviation of the measurement exceeded 30 HU in most conditions. In measurements at the wall center, the attenuation values obtained using MBIR were comparable to or significantly closer to the actual wall attenuation than those acquired using Detail kernel. Using differentiation curves, we could measure attenuation for models with walls of 1.0- or 1.5-mm thickness using MBIR but only those of 1.5-mm thickness using Detail kernel. We detected no significant differences among the attenuation values of the vascular walls of either thickness (MBIR, P = 0.1606) or among the 3 densities of intravascular contrast material (MBIR, P = 0.8185; Detail kernel, P = 0.0802). Conclusions: Compared with FBP, MBIR reduces both reconstruction blur and image noise simultaneously, facilitates recognition of vascular wall boundaries, and can improve accuracy in measuring wall attenuation.

Techniques for measuring aerosol attenuation using the Central Laser Facility at the Pierre Auger Observatory

Energy Technology Data Exchange (ETDEWEB)

Collaboration, The Pierre Auger

2013-04-01

The Pierre Auger Observatory in Malargüe, Argentina, is designed to study the properties of ultra-high energy cosmic rays with energies above 10(18)eV. It is a hybrid facility that employs a Fluorescence Detector to perform nearly calorimetric measurements of Extensive Air Shower energies. To obtain reliable calorimetric information from the FD, the atmospheric conditions at the observatory need to be continuously monitored during data acquisition. In particular, light attenuation due to aerosols is an important atmospheric correction. The aerosol concentration is highly variable, so that the aerosol attenuation needs to be evaluated hourly. We use light from the Central Laser Facility, located near the center of the observatory site, having an optical signature comparable to that of the highest energy showers detected by the FD. This paper presents two procedures developed to retrieve the aerosol attenuation of fluorescence light from CLF laser shots. Cross checks between the two methods demonstrate that results from both analyses are compatible, and that the uncertainties are well understood. The measurements of the aerosol attenuation provided by the two procedures are currently used at the Pierre Auger Observatory to reconstruct air shower data.

Precise Void Fraction Measurement in Two-phase Flows Independent of the Flow Regime Using Gamma-ray Attenuation

Directory of Open Access Journals (Sweden)

E. Nazemi

2016-02-01

Full Text Available Void fraction is an important parameter in the oil industry. This quantity is necessary for volume rate measurement in multiphase flows. In this study, the void fraction percentage was estimated precisely, independent of the flow regime in gas–liquid two-phase flows by using γ-ray attenuation and a multilayer perceptron neural network. In all previous studies that implemented a multibeam γ-ray attenuation technique to determine void fraction independent of the flow regime in two-phase flows, three or more detectors were used while in this study just two NaI detectors were used. Using fewer detectors is of advantage in industrial nuclear gauges because of reduced expense and improved simplicity. In this work, an artificial neural network is also implemented to predict the void fraction percentage independent of the flow regime. To do this, a multilayer perceptron neural network is used for developing the artificial neural network model in MATLAB. The required data for training and testing the network in three different regimes (annular, stratified, and bubbly were obtained using an experimental setup. Using the technique developed in this work, void fraction percentages were predicted with mean relative error of <1.4%.

Materials analysis using x-ray linear attenuation coefficient measurements at four photon energies

International Nuclear Information System (INIS)

Midgley, S M

2005-01-01

The analytical properties of an accurate parameterization scheme for the x-ray linear attenuation coefficient are examined. The parameterization utilizes an additive combination of N compositional- and energy-dependent coefficients. The former were derived from a parameterization of elemental cross-sections using a polynomial in atomic number. The compositional-dependent coefficients are referred to as the mixture parameters, representing the electron density and higher order statistical moments describing elemental distribution. Additivity is an important property of the parameterization, allowing measured x-ray linear attenuation coefficients to be written as linear simultaneous equations, and then solved for the unknown coefficients. The energy-dependent coefficients can be determined by calibration from measurements with materials of known composition. The inverse problem may be utilized for materials analysis, whereby the simultaneous equations represent multi-energy linear attenuation coefficient measurements, and are solved for the mixture parameters. For in vivo studies, the choice of measurement energies is restricted to the diagnostic region (approximately 20 keV to 150 keV), where the parameterization requires N ≥ 4 energies. We identify a mathematical pathology that must be overcome in order to solve the inverse problem in this energy regime. An iterative inversion strategy is presented for materials analysis using four or more measurements, and then tested against real data obtained at energies 32 keV to 66 keV. The results demonstrate that it is possible to recover the electron density to within ±4% and fourth mixture parameter. It is also a key finding that the second and third mixture parameters cannot be recovered, as they are of minor importance in the parameterization at diagnostic x-ray energies

Measurement of vascular wall attenuation: comparison of CT angiography using model-based iterative reconstruction with standard filtered back-projection algorithm CT in vitro.

Science.gov (United States)

Suzuki, Shigeru; Machida, Haruhiko; Tanaka, Isao; Ueno, Eiko

2012-11-01

To compare the performance of model-based iterative reconstruction (MBIR) with that of standard filtered back projection (FBP) for measuring vascular wall attenuation. After subjecting 9 vascular models (actual attenuation value of wall, 89 HU) with wall thickness of 0.5, 1.0, or 1.5 mm that we filled with contrast material of 275, 396, or 542 HU to scanning using 64-detector computed tomography (CT), we reconstructed images using MBIR and FBP (Bone, Detail kernels) and measured wall attenuation at the center of the wall for each model. We performed attenuation measurements for each model and additional supportive measurements by a differentiation curve. We analyzed statistics using analyzes of variance with repeated measures. Using the Bone kernel, standard deviation of the measurement exceeded 30 HU in most conditions. In measurements at the wall center, the attenuation values obtained using MBIR were comparable to or significantly closer to the actual wall attenuation than those acquired using Detail kernel. Using differentiation curves, we could measure attenuation for models with walls of 1.0- or 1.5-mm thickness using MBIR but only those of 1.5-mm thickness using Detail kernel. We detected no significant differences among the attenuation values of the vascular walls of either thickness (MBIR, P=0.1606) or among the 3 densities of intravascular contrast material (MBIR, P=0.8185; Detail kernel, P=0.0802). Compared with FBP, MBIR reduces both reconstruction blur and image noise simultaneously, facilitates recognition of vascular wall boundaries, and can improve accuracy in measuring wall attenuation. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Receiver calibration and the nonlinearity parameter measurement of thick solid samples with diffraction and attenuation corrections.

Science.gov (United States)

Jeong, Hyunjo; Barnard, Daniel; Cho, Sungjong; Zhang, Shuzeng; Li, Xiongbing

2017-11-01

This paper presents analytical and experimental techniques for accurate determination of the nonlinearity parameter (β) in thick solid samples. When piezoelectric transducers are used for β measurements, the receiver calibration is required to determine the transfer function from which the absolute displacement can be calculated. The measured fundamental and second harmonic displacement amplitudes should be modified to account for beam diffraction and material absorption. All these issues are addressed in this study and the proposed technique is validated through the β measurements of thick solid samples. A simplified self-reciprocity calibration procedure for a broadband receiver is described. The diffraction and attenuation corrections for the fundamental and second harmonics are explicitly derived. Aluminum alloy samples in five different thicknesses (4, 6, 8, 10, 12cm) are prepared and β measurements are made using the finite amplitude, through-transmission method. The effects of diffraction and attenuation corrections on β measurements are systematically investigated. When diffraction and attenuation corrections are all properly made, the variation of β between different thickness samples is found to be less than 3.2%. Copyright © 2017 Elsevier B.V. All rights reserved.

Measurement of γ-Ray Attenuation Coefficient for Concrete with Different Aggregate

Energy Technology Data Exchange (ETDEWEB)

Oh, Jeong Hwan [Jeju National University, Jeju (Korea, Republic of); Lee, Jea Hyung; Mun, Young Bum; Choi, Hyun Kook [Sungshin Cement Co, Sejong (Korea, Republic of); Choi, Soo Seok [Jeju National University, Jeju (Korea, Republic of)

2016-05-15

In this work, we used different aggregates in a concrete to examine their effect on gamma-ray shielding. In addition, attenuation coefficient has been evaluated using a gamma-ray measuring system. The attenuation coefficient represents the amount of attenuated radiation by the thickness of a given sample material. Shielding performance improvement is expected to effect on the increasing high-weight aggregate rather than unit weigh and it is consider that additional research is needed for mixing condition of aggregates. In this study, shielding performance of concrete was confirmed to increase, according to the increasing in unit weight and aggregate. However, Iron ore is the density greater than oxidizing slag gravel, but attenuation coefficient is lower than including oxidizing slag gravel. The demand of radiation shielding material for a safe transport and storage of radioactive materials increases rapidly with the commencement of the medium and low-level radioactive waste disposal facility. It is because radioactive materials from a nuclear reactor, spent nuclear fuels, fission products, and many industrial application of radiation influences on environment over a long period by releasing gamma-ray and neutron continuously. Typical radiation shielding materials are lead, boron, iron, water, heavy-weight concrete, etc. In heavy-weight concrete, oxidizing slag from an electric arc furnace, magnetite and barite are used as an aggregate. The radiation shielding rate of the heavy-weight concrete which used oxidizing slag was studied. Both size of coarse aggregate and experiment sample is a few cm thicknesses. Therefore, location of shielding material including metal component in sample is important, according to direction of radiation.

Measuring the attenuation length of water in the CHIPS-M water Cherenkov detector

Energy Technology Data Exchange (ETDEWEB)

Amat, F.; Bizouard, P. [Aix Marseille University Saint-Jerome, 13013 Marseille (France); Bryant, J. [Department of Physics and Astronomy, UCL, Gower St, London WC1E 6BT (United Kingdom); Carroll, T.J.; Rijck, S. De [Department of Physics, University of Texas at Austin, Austin, TX 78712 (United States); Germani, S. [Department of Physics and Astronomy, UCL, Gower St, London WC1E 6BT (United Kingdom); Joyce, T. [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); Kriesten, B. [Department of Physics, College of William & Mary, Williamsburg, VA 23187 (United States); Marshak, M.; Meier, J. [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); Nelson, J.K. [Department of Physics, College of William & Mary, Williamsburg, VA 23187 (United States); Perch, A.J.; Pfützner, M.M. [Department of Physics and Astronomy, UCL, Gower St, London WC1E 6BT (United Kingdom); Salazar, R. [Department of Physics, University of Texas at Austin, Austin, TX 78712 (United States); Thomas, J., E-mail: jennifer.thomas@ucl.ac.uk [Department of Physics and Astronomy, UCL, Gower St, London WC1E 6BT (United Kingdom); Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Trokan-Tenorio, J. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Vahle, P. [Department of Physics, College of William & Mary, Williamsburg, VA 23187 (United States); Wade, R. [Avenir Consulting, Abingdon, Oxfordshire (United Kingdom); Wendt, C. [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States); Whitehead, L.H. [Department of Physics and Astronomy, UCL, Gower St, London WC1E 6BT (United Kingdom); and others

2017-02-01

The water at the proposed site of the CHIPS water Cherenkov detector has been studied to measure its attenuation length for Cherenkov light as a function of filtering time. A scaled model of the CHIPS detector filled with water from the Wentworth 2W pit, proposed site of the CHIPS deployment, in conjunction with a 3.2 m vertical column filled with this water, was used to study the transmission of 405 nm laser light. Results consistent with attenuation lengths of up to 100 m were observed for this wavelength with filtration and UV sterilization alone.

Attenuation on an Earth-space path measured in the wavelength range of 8 to 14 micrometers.

Science.gov (United States)

Wilson, R W

1970-06-19

A telescope operating over the wavelength range of 8 to 14 micrometers has been added to the Crawford Hill sun tracker for the purpose of measuring attenuation in that atmospheric window. Over a 9-month period the attenuation (typically from clouds) exceeded 10, 20, and 30 decibels for 48, 43, and 34 percent of the time.

Determination of the mass attenuation coefficients for X-ray fluorescence measurements correction by the Rayleigh to Compton scattering ratio

Energy Technology Data Exchange (ETDEWEB)

Conti, C.C., E-mail: ccconti@ird.gov.br [Institute for Radioprotection and Dosimetry – IRD/CNEN, Rio de Janeiro (Brazil); Physics Institute, State University of Rio de Janeiro – UERJ, Rio de Janeiro (Brazil); Anjos, M.J. [Physics Institute, State University of Rio de Janeiro – UERJ, Rio de Janeiro (Brazil); Salgado, C.M. [Nuclear Engineering Institute – IEN/CNEN, Rio de Janeiro (Brazil)

2014-09-15

Highlights: •This work describes a procedure for sample self-absorption correction. •The use of Monte Carlo simulation to calculate the mass attenuation coefficients curve was effective. •No need for transmission measurement, saving time, financial resources and effort. •This article provides de curves for the 90° scattering angle. •Calculation on-line at (www.macx.net.br). -- Abstract: X-ray fluorescence technique plays an important role in nondestructive analysis nowadays. The development of equipment, including portable ones, enables a wide assortment of possibilities for analysis of stable elements, even in trace concentrations. Nevertheless, despite of the advantages, one important drawback is radiation self-attenuation in the sample being measured, which needs to be considered in the calculation for the proper determination of elemental concentration. The mass attenuation coefficient can be determined by transmission measurement, but, in this case, the sample must be in slab shape geometry and demands two different setups and measurements. The Rayleigh to Compton scattering ratio, determined from the X-ray fluorescence spectrum, provides a link to the mass attenuation coefficient by means of a polynomial type equation. This work presents a way to construct a Rayleigh to Compton scattering ratio versus mass attenuation coefficient curve by using the MCNP5 Monte Carlo computer code. The comparison between the calculated and literature values of the mass attenuation coefficient for some known samples showed to be within 15%. This calculation procedure is available on-line at (www.macx.net.br)

Mapping Pn amplitude spreading and attenuation in Asia

Energy Technology Data Exchange (ETDEWEB)

Yang, Xiaoning [Los Alamos National Laboratory; Phillips, William S [Los Alamos National Laboratory; Stead, Richard J [Los Alamos National Laboratory

2010-12-06

Pn travels most of its path in the mantle lid. Mapping the lateral variation of Pn amplitude attenuation sheds light on material properties and dynamics of the uppermost region of the mantle. Pn amplitude variation depends on the wavefront geometric spreading as well as material attenuation. We investigated Pn geometric spreading, which is much more complex than a traditionally assumed power-law spreading model, using both synthetic and observed amplitude data collected in Asia. We derived a new Pn spreading model based on the formulation that was proposed previously to account for the spherical shape of the Earth (Yang et. al., BSSA, 2007). New parameters derived for the spreading model provide much better correction for Pn amplitudes in terms of residual behavior. Because we used observed Pn amplitudes to construct the model, the model incorporates not only the effect of the Earth's spherical shape, but also the effect of potential upper-mantle velocity gradients in the region. Using the new spreading model, we corrected Pn amplitudes measured at 1, 2, 4 and 6 Hz and conducted attenuation tomography. The resulting Pn attenuation model correlates well with the regional geology. We see high attenuation in regions such as northern Tibetan Plateau and the western Pacific subduction zone, and low attenuation for stable blocks such as Sichuan and Tarim basins.

Gamma ray attenuation coefficient measurement for neutron-absorbent materials

International Nuclear Information System (INIS)

Jalali, Majid; Mohammadi, Ali

2008-01-01

The compounds Na 2 B 4 O 7 , H 3 BO 3 , CdCl 2 and NaCl and their solutions attenuate gamma rays in addition to neutron absorption. These compounds are widely used in the shielding of neutron sources, reactor control and neutron converters. Mass attenuation coefficients of gamma related to the four compounds aforementioned, in energies 662, 778.9, 867.38, 964.1, 1085.9, 1173, 1212.9, 1299.1,1332 and 1408 keV, have been determined by the γ rays transmission method in a good geometry setup; also, these coefficients were calculated by MCNP code. A comparison between experiments, simulations and Xcom code has shown that the study has potential application for determining the attenuation coefficient of various compound materials. Experiment and computation show that H 3 BO 3 with the lowest average Z has the highest gamma ray attenuation coefficient among the aforementioned compounds

Spinal axis irradiation with electrons: Measurements of attenuation by the spinal processes

International Nuclear Information System (INIS)

Muller-Runkel, R.; Vijayakumar, S.

1986-01-01

Electrons may be used beneficially for spinal axis irradiation in medulloblastoma children to avoid some of the long-term sequelae induced by megavoltage photons. However, the attenuation by the intervening bone ought to be considered. Three-dimensional computer treatment planning with inhomogeneity correction for electron beams is not yet generally available, and alternate methods are needed to evaluate the attenuation by the complex bony structure of the spine. Here, we present our experimental data showing the alteration in the electron isodoses due to the intervening spinous processes. Film dosimetric measurements were made in the vertebral columns obtained from autopsies of a goat, a dog, and a child. Our results show that electron beam therapy for the spinal axis is a viable option

Gamma ray attenuation coefficient measurement for neutron-absorbent materials

Energy Technology Data Exchange (ETDEWEB)

Jalali, Majid [Isfahan Nuclear Science and Technology Research Institute (NSTRT), Reactor and Accelerators Research and Development School, Atomic Energy Organization (Iran, Islamic Republic of)], E-mail: m_jalali@entc.org.ir; Mohammadi, Ali [Faculty of Science, Department of Physics, University of Kashan, Km. 6, Ravand Road, Kashan (Iran, Islamic Republic of)

2008-05-15

The compounds Na{sub 2}B{sub 4}O{sub 7}, H{sub 3}BO{sub 3}, CdCl{sub 2} and NaCl and their solutions attenuate gamma rays in addition to neutron absorption. These compounds are widely used in the shielding of neutron sources, reactor control and neutron converters. Mass attenuation coefficients of gamma related to the four compounds aforementioned, in energies 662, 778.9, 867.38, 964.1, 1085.9, 1173, 1212.9, 1299.1,1332 and 1408 keV, have been determined by the {gamma} rays transmission method in a good geometry setup; also, these coefficients were calculated by MCNP code. A comparison between experiments, simulations and Xcom code has shown that the study has potential application for determining the attenuation coefficient of various compound materials. Experiment and computation show that H{sub 3}BO{sub 3} with the lowest average Z has the highest gamma ray attenuation coefficient among the aforementioned compounds.

Determination of the mass attenuation coefficients for X-ray fluorescence measurements correction by the Rayleigh to Compton scattering ratio

Science.gov (United States)

Conti, C. C.; Anjos, M. J.; Salgado, C. M.

2014-09-01

X-ray fluorescence technique plays an important role in nondestructive analysis nowadays. The development of equipment, including portable ones, enables a wide assortment of possibilities for analysis of stable elements, even in trace concentrations. Nevertheless, despite of the advantages, one important drawback is radiation self-attenuation in the sample being measured, which needs to be considered in the calculation for the proper determination of elemental concentration. The mass attenuation coefficient can be determined by transmission measurement, but, in this case, the sample must be in slab shape geometry and demands two different setups and measurements. The Rayleigh to Compton scattering ratio, determined from the X-ray fluorescence spectrum, provides a link to the mass attenuation coefficient by means of a polynomial type equation. This work presents a way to construct a Rayleigh to Compton scattering ratio versus mass attenuation coefficient curve by using the MCNP5 Monte Carlo computer code. The comparison between the calculated and literature values of the mass attenuation coefficient for some known samples showed to be within 15%. This calculation procedure is available on-line at www.macx.net.br.

Detecting The EBL Attenuation Of Blazars With GLAST

Science.gov (United States)

Reyes, Luis C.

2006-09-01

The Large Area Telescope (LAT) on board GLAST (Gamma-ray Large Area Space Telescope) due for launch in Fall 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 Blazars from about 100 to thousands, with redshifts up to z 5. Since Gamma 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 to the optical-UV EBL density and its evolution over cosmic history. Based on the GLAST-LAT instrument performance, detailed simulations of expected blazar populations attenuated by EBL have been performed. In this poster we present an analysis of such simulations in order to measure the EBL attenuation, ensuing a clear distinction between competing EBL models.

Measurement of current drive profile using electron cyclotron wave attenuation near the O-mode cutoff

International Nuclear Information System (INIS)

Fidone, I.; Meyer, R.L.; Caron, X.

1992-01-01

A method for determining the radial profile of the lower-hybrid current drive in tokamaks using electron cyclotron attenuation of the O mode for frequencies ω near the cutoff frequency is discussed. The basic idea is that, for a given wave frequency, the cutoff plays the role of a spatial filter selecting a variable portion of the noninductive current. It is shown that the incremental attenuation resulting from a small increase of ω displays specific features related to the current density near the cutoff point. Using the relation between the wave damping and the current density, it is possible to determine the radial profile of the current drive from the wave attenuation measurements. A numerical application is also presented for plasma parameters in the reactor regime

Attenuated Vector Tomography -- An Approach to Image Flow Vector Fields with Doppler Ultrasonic Imaging

International Nuclear Information System (INIS)

Huang, Qiu; Peng, Qiyu; Huang, Bin; Cheryauka, Arvi; Gullberg, Grant T.

2008-01-01

The measurement of flow obtained using continuous wave Doppler ultrasound is formulated as a directional projection of a flow vector field. When a continuous ultrasound wave bounces against a flowing particle, a signal is backscattered. This signal obtains a Doppler frequency shift proportional to the speed of the particle along the ultrasound beam. This occurs for each particle along the beam, giving rise to a Doppler velocity spectrum. The first moment of the spectrum provides the directional projection of the flow along the ultrasound beam. Signals reflected from points further away from the detector will have lower amplitude than signals reflected from points closer to the detector. The effect is very much akin to that modeled by the attenuated Radon transform in emission computed tomography.A least-squares method was adopted to reconstruct a 2D vector field from directional projection measurements. Attenuated projections of only the longitudinal projections of the vector field were simulated. The components of the vector field were reconstructed using the gradient algorithm to minimize a least-squares criterion. This result was compared with the reconstruction of longitudinal projections of the vector field without attenuation. If attenuation is known, the algorithm was able to accurately reconstruct both components of the full vector field from only one set of directional projection measurements. A better reconstruction was obtained with attenuation than without attenuation implying that attenuation provides important information for the reconstruction of flow vector fields.This confirms previous work where we showed that knowledge of the attenuation distribution helps in the reconstruction of MRI diffusion tensor fields from fewer than the required measurements. In the application of ultrasound the attenuation distribution is obtained with pulse wave transmission computed tomography and flow information is obtained with continuous wave Doppler

Two-phase flow void fraction measurement using gamma ray attenuation technique

International Nuclear Information System (INIS)

Silva, R.D. da.

1985-01-01

The present work deals with experimental void fraction measurements in two-phase water-nitrogen flow, by using a gamma ray attenuation technique. Several upward two-phase flow regimes in a vertical tube were simulated. The water flow was varied from 0.13 to 0.44 m 3 /h while the nitrogen flow was varied between 0.01 and 0.1 m 3 /h. The mean volumetric void fraction was determined based on the measured linear void fraction for each flow condition. The results were compared with other authors data and showed a good agreement. (author) [pt

Effect of attenuation by the cranium on quantitative SPECT measurements of cerebral blood flow and a correction method

International Nuclear Information System (INIS)

Iwase, Mikio; Kurono, Kenji; Iida, Akihiko.

1998-01-01

Attenuation correction for cerebral blood flow SPECT image reconstruction is usually performed by considering the head as a whole to be equivalent to water, and the effects of differences in attenuation between subjects produced by the cranium have not been taken into account. We determined the differences in attenuation between subjects and assessed a method of correcting quantitative cerebral blood flow values. Attenuations by head on the right and left sides were measured before intravenous injection of 123 I-IMP, and water-converted diameters of both sides (Ta) were calculated from the measurements obtained. After acquiring SPECT images, attenuation correction was conducted according to the method of Sorenson, and images were reconstructed. The diameters of the right and left sides in the same position as the Ta (Tt) were calculated from the contours determined by threshold values. Using Ts given by 2 Ts=Ta-Tt, the correction factor λ=exp(μ 1 Ts) was calculated and multiplied as the correction factor when rCBF was determined. The results revealed significant differences between Tt and Ta. Although no gender differences were observed in Tt, they were seen in both Ta and Ts. Thus, interindividual differences in attenuation by the cranium were found to have an influence that cannot be ignored. Inter-subject correlation is needed to obtain accurate quantitative values. (author)

Measurement of linear attenuation coefficient of different materials

International Nuclear Information System (INIS)

Ali, M. M.

2013-07-01

In this research we study the linear attenuation coefficient from the materials concrete, brick, mixture concrete and iron. In the secondary standard dosimetry laboratory in Atomic Energy from different distance by use Cs-137 sours, chamber farmer 2675 A-600 cc-S/N 0511, and electrometer 2670 A-S/N 114. Found the value of linear attenuation coefficient of concert in the range 0.167 cm -1 , the brick in the range 0.063 -1 and mixture concrete and iron in the range 0.253cm -1 .(Author)

Spectroscopic Measurements of the Far-Ultraviolet Dust Attenuation Curve at z ˜ 3

Science.gov (United States)

Reddy, Naveen A.; Steidel, Charles C.; Pettini, Max; Bogosavljević, Milan

2016-09-01

We present the first spectroscopic measurements of the shape of the far-ultraviolet (far-UV; λ =950{--}1500 Å) dust attenuation curve at high redshift (z˜ 3). Our analysis employs rest-frame UV spectra of 933 galaxies at z˜ 3, 121 of which have very deep spectroscopic observations (≳ 7 hr) at λ =850{--}1300 \\mathring{{A}} , with the Low Resolution Imaging Spectrograph on the Keck Telescope. By using an iterative approach in which we calculate the ratios of composite spectra in different bins of continuum color excess, E(B-V), we derive a dust curve that implies a lower attenuation in the far-UV for a given E(B-V) than those obtained with standard attenuation curves. We demonstrate that the UV composite spectra of z˜ 3 galaxies can be modeled well by assuming our new attenuation curve, a high covering fraction of H I, and absorption from the Lyman-Werner bands of {{{H}}}2 with a small (≲ 20 % ) covering fraction. The low covering fraction of {{{H}}}2 relative to that of the {{H}} {{I}} and dust suggests that most of the dust in the ISM of typical galaxies at z˜ 3 is unrelated to the catalysis of {{{H}}}2, and is associated with other phases of the ISM (I.e., the ionized and neutral gas). The far-UV dust curve implies a factor of ≈ 2 lower dust attenuation of Lyman continuum (ionizing) photons relative to those inferred from the most commonly assumed attenuation curves for L* galaxies at z˜ 3. Our results may be utilized to assess the degree to which ionizing photons are attenuated in H II regions or, more generally, in the ionized or low column density (N({{H}} {{I}})≲ {10}17.2 cm-2) neutral ISM of high-redshift galaxies. Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W.M. Keck Foundation.

Comparison of measured and satellite-derived spectral diffuse attenuation coefficients for the Arabian Sea

Digital Repository Service at National Institute of Oceanography (India)

Suresh, T.; Talaulikar, M.; Desa, E.; Matondkar, S.G.P.; Mascarenhas, A.

The results of study comparing the spectral diffuse attenuation coefficients Kd(Lambda) measured in the Arabian Sea with those derived from the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) using three algorithms, of which two are empirical...

Reliability of computed tomography measurements in assessment of thigh muscle cross-sectional area and attenuation

International Nuclear Information System (INIS)

Strandberg, Sören; Wretling, Marie-Louise; Wredmark, Torsten; Shalabi, Adel

2010-01-01

Advancement in technology of computer tomography (CT) and introduction of new medical imaging softwares enables easy and rapid assessment of muscle cross-sectional area (CSA) and attenuation. Before using these techniques in clinical studies there is a need for evaluation of the reliability of the measurements. The purpose of the study was to evaluate the inter- and intra-observer reliability of ImageJ in measuring thigh muscles CSA and attenuation in patients with anterior cruciate ligament (ACL) injury by computer tomography. 31 patients from an ongoing study of rehabilitation and muscle atrophy after ACL reconstruction were included in the study. Axial CT images with slice thickness of 10 mm at the level of 150 mm above the knee joint were analyzed by two investigators independently at two times with a minimum of 3 weeks between the two readings using NIH ImageJ. CSA and the mean attenuation of individual thigh muscles were analyzed for both legs. Mean CSA and mean attenuation values were in good agreement both when comparing the two observers and the two replicates. The inter- and intraclass correlation (ICC) was generally very high with values from 0.98 to 1.00 for all comparisons except for the area of semimembranosus. All the ICC values were significant (p < 0,001). Pearson correlation coefficients were also generally very high with values from 0.98 to 1.00 for all comparisons except for the area of semimembranosus (0.95 for intraobserver and 0.92 for interobserver). This study has presented ImageJ as a method to monitor and evaluate CSA and attenuation of different muscles in the thigh using CT-imaging. The method shows an overall excellent reliability with respect to both observer and replicate

Photon attenuation by intensifying screens

International Nuclear Information System (INIS)

Holje, G.

1983-01-01

The photon attenuation by intensifying screens of different chemical composition has been determined. The attenuation of photons between 20 keV and 120 keV was measured by use of a multi-channel analyzer and a broad bremsstrahlung distribution. The attenuation by the intensifying screens was hereby determined simultaneously at many different monoenergetic photon energies. Experimentally determined attenuations were found to agree well with attenuation calculated from mass attenuation coefficients. The attenuation by the screens was also determined at various bremsstrahlung distributions, simulating those occurring behind the patient in various diagnostic X-ray examinations. The high attenuation in some of the intensifying screens form the basis for an analysis of the construction of asymmetric screen pairs. Single screen systems are suggested as a favourable alternative to thick screen pair systems. (Author)

Inter-observer and inter-examination variability of manual vertebral bone attenuation measurements on computed tomography

International Nuclear Information System (INIS)

Pompe, Esther; Lammers, Jan-Willem J.; Jong, Pim A. de; Jong, Werner U. de; Takx, Richard A.P.; Eikendal, Anouk L.M.; Willemink, Martin J.; Mohamed Hoesein, Firdaus A.A.; Oudkerk, Matthijs; Budde, Ricardo P.J.

2016-01-01

To determine inter-observer and inter-examination variability of manual attenuation measurements of the vertebrae in low-dose unenhanced chest computed tomography (CT). Three hundred and sixty-seven lung cancer screening trial participants who underwent baseline and repeat unenhanced low-dose CT after 3 months because of an indeterminate lung nodule were included. The CT attenuation value of the first lumbar vertebrae (L1) was measured in all CTs by one observer to obtain inter-examination reliability. Six observers performed measurements in 100 randomly selected CTs to determine agreement with limits of agreement and Bland-Altman plots and reliability with intraclass correlation coefficients (ICCs). Reclassification analyses were performed using a threshold of 110 HU to define osteoporosis. Inter-examination reliability was excellent with an ICC of 0.92 (p < 0.001). Inter-examination limits of agreement ranged from -26 to 28 HU with a mean difference of 1 ± 14 HU. Inter-observer reliability ICCs ranged from 0.70 to 0.91. Inter-examination variability led to 11.2 % reclassification of participants and inter-observer variability led to 22.1 % reclassification. Vertebral attenuation values can be manually quantified with good to excellent inter-examination and inter-observer reliability on unenhanced low-dose chest CT. This information is valuable for early detection of osteoporosis on low-dose chest CT. (orig.)

Measurements within cloud cavitation by means of X-ray attenuation device

International Nuclear Information System (INIS)

Barouch, G.; Legoupil, S.; Stutz, B.; Woo, R.

2004-01-01

The purpose of this work is to describe the two-phase flow structure of cloud cavitation. The experimental study is performed in a cavitation tunnel equipped with a Venturi-type test section. The flow is investigated by means of an optical probe and a X-ray attenuation device. 24 collimated detectors enable measurement of the instantaneous space fraction of the vapour phase at different locations of the two-phase flow. X-ray intensity measurement mode enables fast data acquisitions (250 Hz). The studied geometry is characterized by a convergent angle of 18 deg. and a divergent angle of 8 deg. It leads to regular large vapour cloud shedding

Combining complexity measures of EEG data: multiplying measures reveal previously hidden information.

Science.gov (United States)

Burns, Thomas; Rajan, Ramesh

2015-01-01

Many studies have noted significant differences among human electroencephalograph (EEG) results when participants or patients are exposed to different stimuli, undertaking different tasks, or being affected by conditions such as epilepsy or Alzheimer's disease. Such studies often use only one or two measures of complexity and do not regularly justify their choice of measure beyond the fact that it has been used in previous studies. If more measures were added to such studies, however, more complete information might be found about these reported differences. Such information might be useful in confirming the existence or extent of such differences, or in understanding their physiological bases. In this study we analysed publically-available EEG data using a range of complexity measures to determine how well the measures correlated with one another. The complexity measures did not all significantly correlate, suggesting that different measures were measuring unique features of the EEG signals and thus revealing information which other measures were unable to detect. Therefore, the results from this analysis suggests that combinations of complexity measures reveal unique information which is in addition to the information captured by other measures of complexity in EEG data. For this reason, researchers using individual complexity measures for EEG data should consider using combinations of measures to more completely account for any differences they observe and to ensure the robustness of any relationships identified.

Air slab-correction for Γ-ray attenuation measurements

Science.gov (United States)

Mann, Kulwinder Singh

2017-12-01

Gamma (γ)-ray shielding behaviour (GSB) of a material can be ascertained from its linear attenuation coefficient (μ, cm-1). Narrow-beam transmission geometry is required for μ-measurement. In such measurements, a thin slab of the material has to insert between point-isotropic γ-ray source and detector assembly. The accuracy in measurements requires that sample's optical thickness (OT) remain below 0.5 mean free path (mfp). Sometimes it is very difficult to produce thin slab of sample (absorber), on the other hand for thick absorber, i.e. OT >0.5 mfp, the influence of the air displaced by it cannot be ignored during μ-measurements. Thus, for a thick sample, correction factor has been suggested which compensates the air present in the transmission geometry. The correction factor has been named as an air slab-correction (ASC). Six samples of low-Z engineering materials (cement-black, clay, red-mud, lime-stone, cement-white and plaster-of-paris) have been selected for investigating the effect of ASC on μ-measurements at three γ-ray energies (661.66, 1173.24, 1332.50 keV). The measurements have been made using point-isotropic γ-ray sources (Cs-137 and Co-60), NaI(Tl) detector and multi-channel-analyser coupled with a personal computer. Theoretical values of μ have been computed using a GRIC2-toolkit (standardized computer programme). Elemental compositions of the samples were measured with Wavelength Dispersive X-ray Fluorescence (WDXRF) analyser. Inter-comparison of measured and computed μ-values, suggested that the application of ASC helps in precise μ-measurement for thick samples of low-Z materials. Thus, this hitherto widely ignored ASC factor is recommended to use in similar γ-ray measurements.

Attenuation length measurements of a liquid scintillator with LabVIEW and reliability evaluation of the device

International Nuclear Information System (INIS)

Gao Long; Yu Boxiang; Ding Yayun

2013-01-01

An attenuation length measurement device was constructed using an oscilloscope and LabVIEW for signal acquisition and processing. The performance of the device has been tested in a variety of ways. The test results show that the set-up has a good stability and high precision (sigma/mean reached 0.4 percent). Besides, the accuracy of the measurement system will decrease by about 17 percent if a filter is used. The attenuation length of a gadolinium-loaded liquid scintillator (Gd-LS) was measured as 15.10±0.35 m where Gd-LS was heavily used in the Daya Bay Neutrino Experiment. In addition, one method based on the Beer-Lambert law was proposed to investigate the reliability of the measurement device, the R-square reached 0.9995. Moreover, three purification methods for Linear Alkyl Benzene (LAB) production were compared in the experiment. (authors)

Uranium soft x-ray total attenuation coefficients

International Nuclear Information System (INIS)

Del Grande, N.K.; Oliver, A.J.

1981-01-01

Uranium total attenuation coefficients were measured continuously from 0.84 to 6.0 keV and at selected higher energies using a vacuum single crystal diffractometer and flow-proportional counter. Statistical fluctuations ranged from 0.5% to 2%. The overall accuracy was 3%. Prominent structure was measured within 20 eV of the M 5 (3.552 keV) and M 4 (3.728 keV) edges. Jump ratios were determined from log-log polynomial fits to data at energies apart from the near-edge regions. These data were compared with calculations based on a relativistic HFS central potential model and with previously tabulated data

Control algorithms for dynamic attenuators

Energy Technology Data Exchange (ETDEWEB)

Hsieh, Scott S., E-mail: sshsieh@stanford.edu [Department of Radiology, Stanford University, Stanford, California 94305 and Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Pelc, Norbert J. [Department of Radiology, Stanford University, Stanford California 94305 and Department of Bioengineering, Stanford University, Stanford, California 94305 (United States)

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

Control algorithms for dynamic attenuators

International Nuclear Information System (INIS)

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 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

Control algorithms for dynamic attenuators.

Science.gov (United States)

Hsieh, Scott S; Pelc, Norbert J

2014-06-01

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. 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. The translating and double wedge attenuators reduce dose by an average of 30% relative to current techniques (bowtie filter with tube current modulation) without

Measurement of current drive profile using electron cyclotron wave attenuation near the O-mode cut-off

International Nuclear Information System (INIS)

Fidone, I.

1991-01-01

A method for determining the radial profile of the lower-hybrid current drive in tokamaks uing electron-cyclotron attenuation of the O-mode for frequencies ω near the cut-off frequency is discussed. The basic idea is that for a given wave frequency, the cut-off plays the role of a spatial filter selecting a variable portion of the non-inductive current. It is shown that the incremental attenuation resulting from a small increase of ω displays specific features related to the current density near the cut-off point. Using the relation between the wave damping and the current density it is possible to determine the radial profile of the current drive from the wave attenuation measurements. A numerical application is also presented for plasma parameters in the reactor regime

Suspended sediment assessment by combining sound attenuation and backscatter measurements - analytical method and experimental validation

Science.gov (United States)

Guerrero, Massimo; Di Federico, Vittorio

2018-03-01

The use of acoustic techniques has become common for estimating suspended sediment in water environments. An emitted beam propagates into water producing backscatter and attenuation, which depend on scattering particles concentration and size distribution. Unfortunately, the actual particles size distribution (PSD) may largely affect the accuracy of concentration quantification through the unknown coefficients of backscattering strength, ks2, and normalized attenuation, ζs. This issue was partially solved by applying the multi-frequency approach. Despite this possibility, a relevant scientific and practical question remains regarding the possibility of using acoustic methods to investigate poorly sorted sediment in the spectrum ranging from clay to fine sand. The aim of this study is to investigate the possibility of combining the measurement of sound attenuation and backscatter to determine ζs for the suspended particles and the corresponding concentration. The proposed method is moderately dependent from actual PSD, thus relaxing the need of frequent calibrations to account for changes in ks2 and ζs coefficients. Laboratory tests were conducted under controlled conditions to validate this measurement technique. With respect to existing approaches, the developed method more accurately estimates the concentration of suspended particles ranging from clay to fine sand and, at the same time, gives an indication on their actual PSD.

Attenuation correction for the large non-human primate brain imaging using microPET

International Nuclear Information System (INIS)

Naidoo-Variawa, S; Lehnert, W; Kassiou, M; Banati, R; Meikle, S R

2010-01-01

Assessment of the biodistribution and pharmacokinetics of radiopharmaceuticals in vivo is often performed on animal models of human disease prior to their use in humans. The baboon brain is physiologically and neuro-anatomically similar to the human brain and is therefore a suitable model for evaluating novel CNS radioligands. We previously demonstrated the feasibility of performing baboon brain imaging on a dedicated small animal PET scanner provided that the data are accurately corrected for degrading physical effects such as photon attenuation in the body. In this study, we investigated factors affecting the accuracy and reliability of alternative attenuation correction strategies when imaging the brain of a large non-human primate (papio hamadryas) using the microPET Focus 220 animal scanner. For measured attenuation correction, the best bias versus noise performance was achieved using a 57 Co transmission point source with a 4% energy window. The optimal energy window for a 68 Ge transmission source operating in singles acquisition mode was 20%, independent of the source strength, providing bias-noise performance almost as good as for 57 Co. For both transmission sources, doubling the acquisition time had minimal impact on the bias-noise trade-off for corrected emission images, despite observable improvements in reconstructed attenuation values. In a [ 18 F]FDG brain scan of a female baboon, both measured attenuation correction strategies achieved good results and similar SNR, while segmented attenuation correction (based on uncorrected emission images) resulted in appreciable regional bias in deep grey matter structures and the skull. We conclude that measured attenuation correction using a single pass 57 Co (4% energy window) or 68 Ge (20% window) transmission scan achieves an excellent trade-off between bias and propagation of noise when imaging the large non-human primate brain with a microPET scanner.

Attenuation of Vrancea events revisited

International Nuclear Information System (INIS)

Radulian, M.; Popa, M.; Grecu, B.; Panza, G.F.

2003-11-01

New aspects of the frequency-dependent attenuation of the seismic waves traveling from Vrancea subcrustal sources toward NW (Transylvanian Basin) and SE (Romanian Plain) are evidenced by the recent experimental data made available by the CALIXTO'99 tomography experiment. The observations validate the previous theoretical computations performed for the assessment, by means of a deterministic approach, of the seismic hazard in Romania. They reveal an essential aspect of the seismic ground motion attenuation, that has important implications on the probabilistic assessment of seismic hazard from Vrancea intermediate-depth earthquakes. The attenuation toward NW is shown to be a much stronger frequency-dependent effect than the attenuation toward SE and the seismic hazard computed by the deterministic approach fits satisfactorily well the observed ground motion distribution in the low-frequency band (< 1 Hz). The apparent contradiction with the historically-based intensity maps arises mainly from a systematic difference in the vulnerability (buildings eigenperiod) of the buildings in the intra- and extra-Carpathians regions. (author)

Seismic attenuation and scattering tomography of rock samples using stochastic wavefields: linking seismology, volcanology, and rock physics.

Science.gov (United States)

Fazio, Marco; De Siena, Luca; Benson, Phillip

2016-04-01

Seismic attenuation and scattering are two attributes that can be linked with porosity and permeability in laboratory experiments. When measuring these two quantities using seismic waveforms recorder at lithospheric and volcanic scales the areas of highest heterogeneity, as batches of melt and zones of high deformation, produce anomalous values of the measured quantities, the seismic quality factor and scattering coefficient. When employed as indicators of heterogeneity and absorption in volcanic areas these anomalous effects become strong indicators of magma accumulation and tectonic boundaries, shaping magmatic chambers and conduit systems. We perform attenuation and scattering measurements and imaging using seismic waveforms produced in laboratory experiments, at frequencies ranging between the kHz and MHz. As attenuation and scattering are measured from the shape of the envelopes, disregarding phases, we are able to connect the observations with the micro fracturing and petrological quantities previously measured on the sample. Connecting the imaging of dry and saturated samples via these novel attributes with the burst of low-period events with increasing saturation and deformation is a challenge. Its solution could plant the seed for better relating attenuation and scattering tomography measurements to the presence of fluids and gas, therefore creating a novel path for reliable porosity and permeability tomography. In particular for volcanoes, being able to relate attenuation/scattering measurements with low-period micro seismicity could deliver new data to settle the debate about if both source and medium can produce seismic resonance.

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

Science.gov (United States)

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.

Radiation-attenuated vaccine for lungworm disease

International Nuclear Information System (INIS)

Singh, C.M.

1977-01-01

The work done at the Indian Veternary Research Institute, Izatnagar, on the development of a vaccine for lungworm diseases is reported. Research work done includes: (1) studies on the epidemiology and the incidence of the lungworm infections, (ii) studies on the radiation-attenuated lungworm Dictyocaulus filaria vaccine, (iii) studies on other parasites using ionizing radiation, (iv) incidence of lungworm infection in sheep in Jammu and Kashmir State, (v) suitable dose of gamma radiation for attenuation, (vi) laboratory studies with radiation-attenuated D. filaria vaccine, (vii) serology of D. filaria infection, (viii) field trials with the radiation-attenuated vaccine, (ix) immune response of previously exposed lambs to vaccination, (x) comparative susceptibility of sheep and goats to infection with D. filaria, (xi) quantitative studies of D. filaria in lambs and (xii) production and supply of lungworm vaccine. (A.K.)

Gain attenuation of gated framing camera

International Nuclear Information System (INIS)

Xiao Shali; Liu Shenye; Cao Zhurong; Li Hang; Zhang Haiying; Yuan Zheng; Wang Liwei

2009-01-01

The theoretic model of framing camera's gain attenuation is analyzed. The exponential attenuation curve of the gain along the pulse propagation time is simulated. An experiment to measure the coefficient of gain attenuation based on the gain attenuation theory is designed. Experiment result shows that the gain follows an exponential attenuation rule with a quotient of 0.0249 nm -1 , the attenuation coefficient of the pulse is 0.00356 mm -1 . The loss of the pulse propagation along the MCP stripline is the leading reason of gain attenuation. But in the figure of a single stripline, the gain dose not follow the rule of exponential attenuation completely, instead, there is a gain increase at the stripline bottom. That is caused by the reflection of the pulse. The reflectance is about 24.2%. Combining the experiment and theory, which design of the stripline MCP can improved the gain attenuation. (authors)

High-frequency attenuation and backscatter measurements of rat blood between 30 and 60 MHz

International Nuclear Information System (INIS)

Huang, Chih-Chung

2010-01-01

There has recently been a great deal of interest in noninvasive high-frequency ultrasound imaging of small animals such as rats due to their being the preferred animal model for gene therapy and cancer research. Improving the interpretation of the obtained images and furthering the development of the imaging devices require a detailed knowledge of the ultrasound attenuation and backscattering of biological tissue (e.g. blood) at high frequencies. In the present study, the attenuation and backscattering coefficients of the rat red blood cell (RBC) suspensions and whole blood with hematocrits ranging from 6% to 40% were measured between 30 and 60 MHz using a modified substitution approach. The acoustic parameters of porcine blood under the same conditions were also measured in order to compare differences in the blood properties between these two animals. For porcine blood, both whole blood and RBC suspension were stirred at a rotation speed of 200 rpm. Three different rotation speeds of 100, 200 and 300 rpm were carried out for rat blood experiments. The attenuation coefficients of both rat and porcine blood were found to increase linearly with frequency and hematocrit (the values of coefficients of determination (r 2 ) are around 0.82-0.97 for all cases). The average attenuation coefficient of rat whole blood with a hematocrit of 40% increased from 0.26 Nepers mm -1 at 30 MHz to 0.47 Nepers mm -1 at 60 MHz. The maximum backscattering coefficients of both rat and porcine RBC suspensions were between 10% and 15% hematocrits at all frequencies. The fourth-power dependence of backscatter on frequency was approximately valid for rat RBC suspensions with hematocrits between 6% and 40%. However, the frequency dependence of the backscatter estimate deviates from a fourth-power law for porcine RBC suspension with hematocrit higher than 20%. The backscattering coefficient plateaued for hematocrits higher than 15% in porcine blood, but for rat blood it was maximal around a

Electron Attenuation Measurement using Cosmic Ray Muons at the MicroBooNE LArTPC

Energy Technology Data Exchange (ETDEWEB)

Meddage, Varuna [Kansas State U., Manhattan

2017-10-01

The MicroBooNE experiment at Fermilab uses liquid argon time projection chamber (LArTPC) technology to study neutrino interactions in argon. A fundamental requirement for LArTPCs is to achieve and maintain a low level of electronegative contaminants in the liquid to minimize the capture of drifting ionization electrons. The attenuation time for the drifting electrons should be long compared to the maximum drift time, so that the signals from particle tracks that generate ionization electrons with long drift paths can be detected efficiently. In this talk we present MicroBooNE measurement of electron attenuation using cosmic ray muons. The result yields a minimum electron 1/e lifetime of 18 ms under typical operating conditions, which is long compared to the maximum drift time of 2.3 ms.

The measurement of attenuation coefficients at low photon energies using fluorescent x-radiation

International Nuclear Information System (INIS)

Peaple, L.H.J.; White, D.R.

1978-03-01

A rapid and accurate method has been developed to measure low energy attenuation coefficients for materials of importance in radiation dosimetry. It employs a collimated beam of fluorescent x-rays from which the required radiation is selected by means of a high resolution germanium detector and multi-channel analyser. The method is described in detail and its accuracy and application outlined with reference to the results from nine different materials. (author)

Partial Sleep Deprivation Attenuates the Positive Affective System: Effects Across Multiple Measurement Modalities.

Science.gov (United States)

Finan, Patrick H; Quartana, Phillip J; Remeniuk, Bethany; Garland, Eric L; Rhudy, Jamie L; Hand, Matthew; Irwin, Michael R; Smith, Michael T

2017-01-01

Ample behavioral and neurobiological evidence links sleep and affective functioning. Recent self-report evidence suggests that the affective problems associated with sleep loss may be stronger for positive versus negative affective state and that those effects may be mediated by changes in electroencepholographically measured slow wave sleep (SWS). In the present study, we extend those preliminary findings using multiple measures of affective functioning. In a within-subject randomized crossover experiment, we tested the effects of one night of sleep continuity disruption via forced awakenings (FA) compared to one night of uninterrupted sleep (US) on three measures of positive and negative affective functioning: self-reported affective state, affective pain modulation, and affect-biased attention. The study was set in an inpatient clinical research suite. Healthy, good sleeping adults (N = 45) were included. Results indicated that a single night of sleep continuity disruption attenuated positive affective state via FA-induced reductions in SWS. Additionally, sleep continuity disruption attenuated the inhibition of pain by positive affect as well as attention bias to positive affective stimuli. Negative affective state, negative affective pain facilitation, nor negative attention bias were altered by sleep continuity disruption. The present findings, observed across multiple measures of affective function, suggest that sleep continuity disruption has a stronger influence on the positive affective system relative to the negative affective affective system. © Sleep Research Society 2016. Published by Oxford University Press on behalf of the Sleep Research Society. All rights reserved. For permissions, please e-mail journals.permissions@oup.com.

Simultaneous measurement of unfrozen water content and ice content in frozen soil using gamma ray attenuation and TDR

Science.gov (United States)

Zhou, Xiaohai; Zhou, Jian; Kinzelbach, Wolfgang; Stauffer, Fritz

2014-12-01

The freezing temperature of water in soil is not constant but varies over a range determined by soil texture. Consequently, the amounts of unfrozen water and ice change with temperature in frozen soil, which in turn affects hydraulic, thermal, and mechanical properties of frozen soil. In this paper, an Am-241 gamma ray source and time-domain reflectometry (TDR) were combined to measure unfrozen water content and ice content in frozen soil simultaneously. The gamma ray attenuation was used to determine total water content. The TDR was used to determine the dielectric constant of the frozen soil. Based on a four-phase mixing model, the amount of unfrozen water content in the frozen soil could be determined. The ice content was inferred by the difference between total water content and unfrozen water content. The gamma ray attenuation and the TDR were both calibrated by a gravimetric method. Water contents measured by gamma ray attenuation and TDR in an unfrozen silt column under infiltration were compared and showed that the two methods have the same accuracy and response to changes of water content. Unidirectional column freezing experiments were performed to apply the combined method of gamma ray attenuation and TDR for measuring unfrozen water content and ice content. The measurement error of the gamma ray attenuation and TDR was around 0.02 and 0.01 m3/m3, respectively. The overestimation of unfrozen water in frozen soil by TDR alone was quantified and found to depend on the amount of ice content. The higher the ice content, the larger the overestimation. The study confirmed that the combined method could accurately determine unfrozen water content and ice content in frozen soil. The results of soil column freezing experiments indicate that total water content distribution is affected by available pore space and the freezing front advance rate. It was found that there is similarity between the soil water characteristic and the soil freezing characteristic of

Unfocused beam patterns in nonattenuating and attenuating fluids

International Nuclear Information System (INIS)

Goldstein, Albert

2004-01-01

The most important aspect of an ultrasound measuring system is knowledge of the transducer beam pattern. At all depths accurate single integral equations have been derived for the full beam pattern of steady state unfocused circular flat piston sources radiating into nonattenuating and attenuating fluids. The axial depth of the beginning of the unattenuated beam pattern far field is found to be at 6.41Y 0 . The unattenuated single integral equations are identical to a Jinc function directivity term at this and deeper depths. For attenuating fluids values of α and z are found that permit the attenuated axial pressure to be represented by a plane wave multiplicative exponential attenuation factor. This knowledge will aid in the experimental design of highly accurate attenuation measurements. Accurate single integral equations for the attenuated full beam pattern are derived using complex Bessel functions

Improvement of quantitation in SPECT: Attenuation and scatter correction using non-uniform attenuation data

International Nuclear Information System (INIS)

Mukai, T.; Torizuka, K.; Douglass, K.H.; Wagner, H.N.

1985-01-01

Quantitative assessment of tracer distribution with single photon emission computed tomography (SPECT) is difficult because of attenuation and scattering of gamma rays within the object. A method considering the source geometry was developed, and effects of attenuation and scatter on SPECT quantitation were studied using phantoms with non-uniform attenuation. The distribution of attenuation coefficients (μ) within the source were obtained by transmission CT. The attenuation correction was performed by an iterative reprojection technique. The scatter correction was done by convolution of the attenuation corrected image and an appropriate filter made by line source studies. The filter characteristics depended on μ and SPEC measurement at each pixel. The SPECT obtained by this method showed the most reasonable results than the images reconstructed by other methods. The scatter correction could compensate completely for a 28% scatter components from a long line source, and a 61% component for thick and extended source. Consideration of source geometries was necessary for effective corrections. The present method is expected to be valuable for the quantitative assessment of regional tracer activity

Modifying Spearman's Attenuation Equation to Yield Partial Corrections for Measurement Error--With Application to Sample Size Calculations

Science.gov (United States)

Nicewander, W. Alan

2018-01-01

Spearman's correction for attenuation (measurement error) corrects a correlation coefficient for measurement errors in either-or-both of two variables, and follows from the assumptions of classical test theory. Spearman's equation removes all measurement error from a correlation coefficient which translates into "increasing the reliability of…

Measurement and analysis. Ultrasonic testing. Study of the attenuation of ultrasonic beams through steels

International Nuclear Information System (INIS)

Canella, G.

1977-01-01

Anisotropy, inclusions, segregations and grain size are factors affecting the mechanical properties of steel and determining, at the same time, attenuation of an untrasonic beam crossing it. A system was developed, which offers guarantees of good reproducibility (within 5%) obtained with a device applying a constant and uniform pressure on the probe and using oil with very low viscosity and surface tension as couplant liquid. This oil, generally used as penetrant, is excellent by the rapidity of its constant response and by the thin layer formed which is free from air bubbles between probe and piece. Measurements of reflection loss were also carried out and investigated about the influence on such loss of: couplant liquid; type of transducer; type of piezoelectric protection. For transducers whose surface is protected by an hard coat loss by reflection (about 1 dB) varies within the measuring error, for the different couplant liquids. For transducers with unprotected sensitive surface, loss depends on the type of crystal and is significantly reduced (from 3 dB to 0,5 dB approximately) with an appropriate rubber layer. In both cases; loss proved to be independent of frequency. The samples were subjected to different heat treatments and, for each measurement of amplitude and frequency attenuation and structure micrographies were carried out. These methods of inspections can be applied in industry without any great difficulty

Single-experiment simultaneous-measurement of elemental mass-attenuation coefficients of hydrogen, carbon and oxygen for 0.123-1.33 MeV gamma rays

International Nuclear Information System (INIS)

Teli, M.T.; Nathuram, R.; Mahajan, C.S.

2000-01-01

As it is inconvenient to use elements like hydrogen, carbon and oxygen in pure forms for measurement of their gamma mass-attenuation coefficients, the measurements are to be done indirectly, by using compounds of the elements or a mixture of them. We give here a simple method of measuring the total mass-attenuation coefficients μ/ρ of the elements in a compound simultaneously and in a single experiment through the measurements of the μ/ρ values of the concerned compounds and using the mixture rule. The method is applied for the measurement of μ/ρ of hydrogen, carbon and oxygen by using acetone, ethanol and 1-propanol. Our results (for E γ =0.123-1.33 MeV) are seen to be in better agreement with the theoretical values of Hubbell and Seltzer (1995) [Hubbell J.H. and Seltzer S.M. (1995). Tables of X-ray mass attenuation coefficients and mass energy-absorption coefficients 1 keV to 20 MeV for elements Z=1 to 92 and 48 additional substances of dosimetric interest. NISTIR 5632] as compared to the results of El-Kateb and Abdul-Hamid (1991) [El-Kateb, A.H., Abdul-Hamid, A.S., 1991. Photon attenuation coefficient study of some materials containing hydrogen, carbon, and oxygen. Appl. Rad. Isot. 42, 303-307

PET attenuation coefficients from CT images: experimental evaluation of the transformation of CT into PET 511-keV attenuation coefficients.

Science.gov (United States)

Burger, C; Goerres, G; Schoenes, S; Buck, A; Lonn, A H R; Von Schulthess, G K

2002-07-01

The CT data acquired in combined PET/CT studies provide a fast and essentially noiseless source for the correction of photon attenuation in PET emission data. To this end, the CT values relating to attenuation of photons in the range of 40-140 keV must be transformed into linear attenuation coefficients at the PET energy of 511 keV. As attenuation depends on photon energy and the absorbing material, an accurate theoretical relation cannot be devised. The transformation implemented in the Discovery LS PET/CT scanner (GE Medical Systems, Milwaukee, Wis.) uses a bilinear function based on the attenuation of water and cortical bone at the CT and PET energies. The purpose of this study was to compare this transformation with experimental CT values and corresponding PET attenuation coefficients. In 14 patients, quantitative PET attenuation maps were calculated from germanium-68 transmission scans, and resolution-matched CT images were generated. A total of 114 volumes of interest were defined and the average PET attenuation coefficients and CT values measured. From the CT values the predicted PET attenuation coefficients were calculated using the bilinear transformation. When the transformation was based on the narrow-beam attenuation coefficient of water at 511 keV (0.096 cm(-1)), the predicted attenuation coefficients were higher in soft tissue than the measured values. This bias was reduced by replacing 0.096 cm(-1) in the transformation by the linear attenuation coefficient of 0.093 cm(-1) obtained from germanium-68 transmission scans. An analysis of the corrected emission activities shows that the resulting transformation is essentially equivalent to the transmission-based attenuation correction for human tissue. For non-human material, however, it may assign inaccurate attenuation coefficients which will also affect the correction in neighbouring tissue.

Attenuation coefficients of soils

International Nuclear Information System (INIS)

Martini, E.; Naziry, M.J.

1989-01-01

As a prerequisite to the interpretation of gamma-spectrometric in situ measurements of activity concentrations of soil radionuclides the attenuation of 60 to 1332 keV gamma radiation by soil samples varying in water content and density has been investigated. A useful empirical equation could be set up to describe the dependence of the mass attenuation coefficient upon photon energy for soil with a mean water content of 10%, with the results comparing well with data in the literature. The mean density of soil in the GDR was estimated at 1.6 g/cm 3 . This value was used to derive the linear attenuation coefficients, their range of variation being 10%. 7 figs., 5 tabs. (author)

New procedures for analyzing Doppler-shift attenuation lifetime measurements

Energy Technology Data Exchange (ETDEWEB)

Petkov, P., E-mail: petkov@inrne.bas.bg [Bulgarian Academy of Sciences, Institute for Nuclear Research and Nuclear Energy, 1784 Sofia (Bulgaria); Dewald, A. [Institut für Kernphysik, Universität zu Köln, D-50937 Köln (Germany); Tonev, D.; Goutev, N.; Asova, G.; Dimitrov, B.; Gavrilov, G.; Mineva, M.N.; Yavahchova, M.S. [Bulgarian Academy of Sciences, Institute for Nuclear Research and Nuclear Energy, 1784 Sofia (Bulgaria)

2015-05-21

A generalization of an earlier proposed version of the Differential decay curve method is presented for the analysis of Doppler-shift attenuation lifetime measurements. The lifetime is derived directly from the line shapes of the depopulating and feeding transitions without any assumptions about or fitting of the time dependence of the population of the corresponding levels except for unobserved feeding when relevant. Fitting of the line shapes is also not necessary. The only approximation involved is related to the continuous treatment of the nuclear scattering events in the Monte Carlo simulation needed. Tests with simulated and real data reveal good reliability of this method. We propose also a new precise procedure where the lifetime is derived by fitting the time dependence of the population of the level of interest using the line shape of the depopulating transition and the difference of the spectra of the depopulating and feeding transitions. Practical application to simulated and real data proves the applicability of the new procedure.

Influence of intracoronary attenuation on coronary plaque measurements using multislice computed tomography: observations in an ex vivo model of coronary computed tomography angiography

International Nuclear Information System (INIS)

Cademartiri, Filippo; Krestin, Gabriel P.; Mollet, Nico R.; Feyter, Pim J. de; Runza, Giuseppe; Midiri, Massimo; Bruining, Nico; Hamers, Ronald; Somers, Pamela; Knaapen, Michiel; Verheye, Stefan

2005-01-01

Assessment of attenuation (measured in Hounsfield units, HU) of human coronary plaques was performed using multislice computed tomography (MSCT) in an ex vivo model. In three ex vivo specimens of left coronary arteries in oil, MSCT was performed after intracoronary injection of four solutions of contrast material (400 mgI/ml iomeprol). The four solutions were diluted as follows: 1/∞, 1/200, 1/80, and 1/20. All scans were performed with the following parameters: slices/collimation 16/0.75 mm, rotation time 375 ms. Each specimen was scored for the presence of atherosclerotic plaques. In each plaque the attenuation was measured in four regions of interest for lumen, plaque (non-calcified thickening of the vessel wall), calcium, and surrounding (oil surrounding the vessel). The results were compared with a one-way analysis of variance test and were correlated with Pearson's test. There were no significant differences in the attenuation of calcium and oil in the four solutions. The mean attenuation in the four solutions for lumen (35±10, 91±7, 246±18, 511±89 HU) and plaque (22±22, 50±26, 107±36, 152±67 HU) was significantly different between each decreasing dilution (p<0.001). The mean attenuation of lumen and plaque of coronary plaques showed high correlation, while the values were significantly different (r=0.73; p<0.001). Intracoronary attenuation modifies significantly the attenuation of plaques assessed with MSCT. (orig.)

Empirical Relations for Optical Attenuation Prediction from Liquid Water Content of Fog

Directory of Open Access Journals (Sweden)

M. S. Khan

2012-09-01

Full Text Available Simultaneous measurements of the liquid water content (LWC and optical attenuation have been analyzed to predict optical attenuation caused by fog particles. Attenuation has been measured at two different wavelengths, 830 nm and 1550 nm, across co-located links. Five months measured data have been processed to assess power-law empirical models, which estimate optical attenuation from the LWC. The proposed models are compared with other published models and are demonstrated to perform sufficiently well to predict optical attenuation if the LWC values are available.

Ultrasonic attenuation measurements at very high SNR: Correlation, information theory and performance

International Nuclear Information System (INIS)

Challis, Richard; Ivchenko, Vladimir; Al-Lashi, Raied

2013-01-01

This paper describes a system for ultrasonic wave attenuation measurements which is based on pseudo-random binary codes as transmission signals combined with on-the-fly correlation for received signal detection. The apparatus can receive signals in the nanovolt range against a noise background in the order of hundreds of microvolts and an analogue to digital convertor (ADC) bit-step also in the order of hundreds of microvolts. Very high signal to noise ratios (SNRs) are achieved without recourse to coherent averaging with its associated requirement for high sampling times. The system works by a process of dithering – in which very low amplitude received signals enter the dynamic range of the ADC by 'riding' on electronic noise at the system input. The amplitude of this 'useful noise' has to be chosen with care for an optimised design. The process of optimisation is explained on the basis of classical information theory and is achieved through a simple noise model. The performance of the system is examined for different transmitted code lengths and gain settings in the receiver chain. Experimental results are shown to verify the expected operation when the system is applied to a very highly attenuating material – an aerated slurry

Calculation of the flux attenuation and multiple scattering correction factors in time of flight technique for double differential cross section measurements

International Nuclear Information System (INIS)

Martin, G.; Coca, M.; Capote, R.

1996-01-01

Using Monte Carlo method technique , a computer code which simulates the time of flight experiment to measure double differential cross section was developed. The correction factor for flux attenuation and multiple scattering, that make a deformation to the measured spectrum, were calculated. The energy dependence of the correction factor was determined and a comparison with other works is shown. Calculations for Fe 56 at two different scattering angles were made. We also reproduce the experiment performed at the Nuclear Analysis Laboratory for C 12 at 25 celsius degree and the calculated correction factor for the is measured is shown. We found a linear relation between the scatter size and the correction factor for flux attenuation

Effective radiation attenuation calibration for breast density: compression thickness influences and correction

Directory of Open Access Journals (Sweden)

Thomas Jerry A

2010-11-01

Full Text Available Abstract Background Calibrating mammograms to produce a standardized breast density measurement for breast cancer risk analysis requires an accurate spatial measure of the compressed breast thickness. Thickness inaccuracies due to the nominal system readout value and compression paddle orientation induce unacceptable errors in the calibration. Method A thickness correction was developed and evaluated using a fully specified two-component surrogate breast model. A previously developed calibration approach based on effective radiation attenuation coefficient measurements was used in the analysis. Water and oil were used to construct phantoms to replicate the deformable properties of the breast. Phantoms consisting of measured proportions of water and oil were used to estimate calibration errors without correction, evaluate the thickness correction, and investigate the reproducibility of the various calibration representations under compression thickness variations. Results The average thickness uncertainty due to compression paddle warp was characterized to within 0.5 mm. The relative calibration error was reduced to 7% from 48-68% with the correction. The normalized effective radiation attenuation coefficient (planar representation was reproducible under intra-sample compression thickness variations compared with calibrated volume measures. Conclusion Incorporating this thickness correction into the rigid breast tissue equivalent calibration method should improve the calibration accuracy of mammograms for risk assessments using the reproducible planar calibration measure.

Attenuation in Melting Layer of Precipitation

NARCIS (Netherlands)

Klaassen, W.

1988-01-01

A model of the melting layer is employed on radar measurements to simulate the attenuation of radio waves at 12, 20 and 30GHz. The attenuation in the melting layer is simulated to be slightly larger than that of rain with the same path length and precipitation intensity. The result appears to depend

Self-attenuation factors in gamma-ray spectrometry

International Nuclear Information System (INIS)

Korun, M.

1999-01-01

The relation between the self-attenuation factors and the distribution function describing the number of photons detected in the full-energy peaks, as a function of their path length in the sample is presented. The relations between the self-attenuation factor and the moments of the distribution function, the average path length and the variance are also presented. The use of these relations is illustrated by applying them to self-attenuation factors describing attenuation in cylindrical samples. The results of the calculations are compared with the measured average path lengths and discussed in terms of the properties of the distribution function. (author)

Measurement of mass attenuation coefficients of moderate-to-high atomic-number elements at low photon energies

International Nuclear Information System (INIS)

Tajuddin, A.A.; Chong, C.S.; Shukri, A.; Bradley, D.A.

1995-01-01

Mass attenuation coefficients for 12 selected moderate-to-high atomic-number elements have been obtained from good-geometry measurements made at five 241 Am photon energies of significant emission intensity. Particular interest focuses on measured values for photon energies close to absorption edges. Comparisons with renormalized cross-section predictions indicate agreement to within stated error limits for the majority of cases. Significant discrepancies (> 10%) are noted for Ta at 17.8 and 26.3 keV and W at 59.5 keV. Some support for a discrepancy between measurement and theory for W in the region of 60 keV is found in the reported measurements of others. (author)

Spatially resolved ultrasonic attenuation in resistance spot welds: implications for nondestructive testing.

Science.gov (United States)

Mozurkewich, George; Ghaffari, Bita; Potter, Timothy J

2008-09-01

Spatial variation of ultrasonic attenuation and velocity has been measured in plane parallel specimens extracted from resistance spot welds. In a strong weld, attenuation is larger in the nugget than in the parent material, and the region of increased attenuation is surrounded by a ring of decreased attenuation. In the center of a stick weld, attenuation is even larger than in a strong weld, and the low-attenuation ring is absent. These spatial variations are interpreted in terms of differences in grain size and martensite formation. Measured frequency dependences indicate the presence of an additional attenuation mechanism besides grain scattering. The observed attenuations do not vary as commonly presumed with weld quality, suggesting that the common practice of using ultrasonic attenuation to indicate weld quality is not a reliable methodology.

Self-attenuation correction factors for bioindicators measured by γ spectrometry for energies <100keV

International Nuclear Information System (INIS)

Manduci, L.; Tenailleau, L.; Trolet, J.L.; De Vismes, A.; Lopez, G.; Piccione, M.

2010-01-01

The mass attenuation coefficients for a number of marine and terrestrial bioindicators were measured using γ spectrometry for energies between 22 and 80 keV. These values were then used to find the correction factor k for the apparent radioactivity. The experimental results were compared with a Monte Carlo simulation performed using PENELOPE in order to evaluate the reliability of the simplified calculation and to determine the correction factors.

A practical attenuation compensation method for cone beam spect

International Nuclear Information System (INIS)

Manglos, S.H.; Jaszczak, R.J.; Floyd, C.E.; Greer, K.L.; Coleman, R.E.

1987-01-01

An algorithm for attenuation compensation of cone beam SPECT images has been developed and implemented. The algorithm is based on a multiplicative post-processing method previously used for parallel and fan beam geometries. This method computes the compensation from the estimated average attenuation of photons originating from each image pixel. In the present development, a uniform attenuation coefficient inside of the body contour is assumed, although the method could be extended to include a non-uniform attenuation map. The algorithm is tested with experimental projections of a phantom obtained using a cone beam collimator. Profiles through the reconstructed images are presented as a quantitative test of the improvement due to the compensation. The algorithm provides adequate compensation for attenuation in a simple uniform cylindrical phantom, and the computational time is short compared to that expected for iterative reconstruction techniques. Also observed are image distortions in some reconstructed slices when the source distribution extends beyond the edge of the cone beam axial field-of-view

Measurement of X-ray mass attenuation coefficient of nickel around the K-edge using synchrotron radiation based X-ray absorption study

International Nuclear Information System (INIS)

Roy, Bunty Rani; Rajput, Parasmani; Jha, S.N.; Nageswara Rao, A.S.

2015-01-01

The work presents the X-ray absorption fine structure (XAFS) technique for measuring the X-ray mass attenuation coefficient of nickel metal foil in the X-ray energy range of 8271.2–8849.4 eV using scanning XAFS beam line (BL-09) at Indus-2 synchrotron radiation source facility, Raja Ramanna Centre for Advanced Technology (RRCAT) at Indore, India. The result represents the X-ray mass attenuation coefficient data for 0.02 mm thick Ni metal foil in the XAFS region of Ni K-edge. However, the results are compared to theoretical values using X-COM. There is a maximum deviation which is found exactly near the K-edge jump and decreases as we move away from the absorption edge. Oscillatory structure appears just above the observed absorption edge i.e., 8348.7 eV and is confined to around 250 eV above the edge. - Highlights: • Mass attenuation coefficient measurements of nickel using synchrotron radiation. • The measurements were taken exactly near the Ni K-edge at an energy step of 1 eV. • A maximum deviation is found near the K-edge

Measurement of mass attenuation coefficients around the K absorption edge by parametric X-rays

International Nuclear Information System (INIS)

Tamura, Masaya; Akimoto, Tadashi; Aoki, Yohei; Ikeda, Jiro; Sato, Koichi; Fujita, Fumiyuki; Homma, Akira; Sawamura, Teruko; Narita, Masakuni

2002-01-01

When electrons at relativistic velocities pass through a crystal plate, such as silicon, photons are emitted around the Bragg angle for X-ray diffraction. This phenomenon is called parametric X-ray radiation (PXR). The monochromaticity and directivity of PXR are adequate and the energy can be changed continuously by rotating the crystal. This study measured the mass attenuation coefficient around the K-shell absorption edge of Nb, Zr and Mo as a PXR application of monochromatic hard X-ray radiation sources

Measurement of mass attenuation coefficients around the K absorption edge by parametric X-rays

CERN Document Server

Tamura, M; Aoki, Y; Ikeda, J; Sato, K; Fujita, F; Homma, A; Sawamura, T; Narita, M

2002-01-01

When electrons at relativistic velocities pass through a crystal plate, such as silicon, photons are emitted around the Bragg angle for X-ray diffraction. This phenomenon is called parametric X-ray radiation (PXR). The monochromaticity and directivity of PXR are adequate and the energy can be changed continuously by rotating the crystal. This study measured the mass attenuation coefficient around the K-shell absorption edge of Nb, Zr and Mo as a PXR application of monochromatic hard X-ray radiation sources.

In-situ measurement of the light attenuation in liquid argon in the GERDA cryostat

Energy Technology Data Exchange (ETDEWEB)

Schneider, Birgit [TU Dresden, Institut fuer Kern- und Teilchenphysik (Germany); Collaboration: GERDA-Collaboration

2016-07-01

GERDA is an experiment searching for neutrinoless double beta decay in {sup 76}Ge. It operates the enriched germanium detectors bare in liquid argon (LAr), which serves both as a coolant and a shield for external radiation. Phase II of GERDA aims for an exposure of 100 kg . yr with a background index (BI) of 10{sup -3} cts/(kg . yr . keV). One of the major improvements to further reduce the BI comes from the instrumentation of the LAr to readout its scintillation light. The attenuation of the scintillation light in LAr limits the effective active volume of the LAr veto and is therefore a key parameter to characterize the instrumentation. In order to measure the light attenuation in LAr, a setup was designed that could be deployed directly into the GERDA cryostat. This setup contains a movable beta source and a PMT to detect the scintillation light at different distances. The talk will present the acquired data as well as a detailed description of the performed analysis technique and the current results.

Precision Model for Microwave Rotary Vane Attenuator

DEFF Research Database (Denmark)

Guldbrandsen, Tom

1979-01-01

A model for a rotary vane attenuator is developed to describe the attenuator reflection and transmission coefficients in detail. All the parameters of the model can be measured in situ, i.e., without diassembling any part. The tranmission errors caused by internal reflections are calculated from ...

Determination of the attenuation map in emission tomography

CERN Document Server

Zaidi, H

2002-01-01

Reliable attenuation correction methods for quantitative emission computed tomography (ECT) require accurate delineation of the body contour and often necessitate knowledge of internal anatomical structure. Two broad classes of methods have been used to calculate the attenuation map referred to as "transmissionless" and transmission-based attenuation correction techniques. While calculated attenuation correction belonging to the first class of methods is appropriate for brain studies, more adequate methods must be performed in clinical applications where the attenuation coefficient distribution is not known a priori, and for areas of inhomogeneous attenuation such as the chest. Measured attenuation correction overcomes this problem and utilizes different approaches to determine this map including transmission scanning, segmented magnetic resonance images or appropriately scaled X-ray CT scans acquired either independently on separate or simultaneously on multimodality imaging systems. Combination of data acqu...

Segmented attenuation correction using artificial neural networks in positron tomography

International Nuclear Information System (INIS)

Yu, S.K.; Nahmias, C.

1996-01-01

The measured attenuation correction technique is widely used in cardiac positron tomographic studies. However, the success of this technique is limited because of insufficient counting statistics achievable in practical transmission scan times, and of the scattered radiation in transmission measurement which leads to an underestimation of the attenuation coefficients. In this work, a segmented attenuation correction technique has been developed that uses artificial neural networks. The technique has been validated in phantoms and verified in human studies. The results indicate that attenuation coefficients measured in the segmented transmission image are accurate and reproducible. Activity concentrations measured in the reconstructed emission image can also be recovered accurately using this new technique. The accuracy of the technique is subject independent and insensitive to scatter contamination in the transmission data. This technique has the potential of reducing the transmission scan time, and satisfactory results are obtained if the transmission data contain about 400 000 true counts per plane. It can predict accurately the value of any attenuation coefficient in the range from air to water in a transmission image with or without scatter correction. (author)

Quantifying movements of corrosion products in reinforced concrete using x-ray attenuation measurements

DEFF Research Database (Denmark)

Pease, Bradley Justin; Michel, Alexander; Stang, Henrik

2011-01-01

Corrosion of steel reinforcement, embedded in concrete, may substantially degrade concrete structures due to the expansive nature of corrosion products. Expansion of corrosion products cause tensile stresses to develop and cracks to form in concrete. Extensive research has focused on corrosion...... of corrosion products move into the concrete without generating tensile stresses and cracks in the concrete. Typically, corrosion products are thought to occupy pores, interfacial defects, and/or air voids located near the concrete-steel interface and stresses develop only after filling of these pores. Further....... X-ray attenuation measurements are also capable of detecting cracks. Therefore, this approach provides a direct measurement of the amount and location of reinforcement corrosion products required to induce cracking. Results of a parametric investigation on the impact of water-to-cement ratio (0...

Short Daytime Naps Briefly Attenuate Objectively Measured Sleepiness Under Chronic Sleep Restriction.

Science.gov (United States)

Saletin, Jared M; Hilditch, Cassie J; Dement, William C; Carskadon, Mary A

2017-09-01

Napping is a useful countermeasure to the negative effects of acute sleep loss on alertness. The efficacy of naps to recover from chronic sleep loss is less well understood. Following 2 baseline nights (10 hours' time-in-bed), participants were restricted to 7 nights of 5-hour sleep opportunity. Ten adults participated in the No-Nap condition, and a further 9 were assigned to a Nap condition with a daily 45-minute nap opportunity at 1300 h. Sleepiness was assessed using the multiple sleep latency test and a visual analogue scale at 2-hour intervals. Both objective and subjective indexes of sleepiness were normalized within subject as a difference from those at baseline prior to sleep restriction. Mixed-effects models examined how the daytime nap opportunity altered sleepiness across the day and across the protocol. Short daytime naps attenuated sleepiness due to chronic sleep restriction for up to 6-8 hours after the nap. Benefits of the nap did not extend late into evening. Subjective sleepiness demonstrated a similar short-lived benefit that emerged later in the day when objective sleepiness already returned to pre-nap levels. Neither measure showed a benefit of the nap the following morning after the subsequent restriction night. These data indicate a short daytime nap may attenuate sleepiness in chronic sleep restriction, yet subjective and objective benefits emerge at different time scales. Because neither measure showed a benefit the next day, the current study underscores the need for careful consideration before naps are used as routine countermeasures to chronic sleep loss. © Sleep Research Society 2017. Published by Oxford University Press on behalf of the Sleep Research Society. All rights reserved. For permissions, please e-mail journals.permissions@oup.com.

An attenuation correction method for PET/CT images

International Nuclear Information System (INIS)

Ue, Hidenori; Yamazaki, Tomohiro; Haneishi, Hideaki

2006-01-01

In PET/CT systems, accurate attenuation correction can be achieved by creating an attenuation map from an X-ray CT image. On the other hand, respiratory-gated PET acquisition is an effective method for avoiding motion blurring of the thoracic and abdominal organs caused by respiratory motion. In PET/CT systems employing respiratory-gated PET, using an X-ray CT image acquired during breath-holding for attenuation correction may have a large effect on the voxel values, especially in regions with substantial respiratory motion. In this report, we propose an attenuation correction method in which, as the first step, a set of respiratory-gated PET images is reconstructed without attenuation correction, as the second step, the motion of each phase PET image from the PET image in the same phase as the CT acquisition timing is estimated by the previously proposed method, as the third step, the CT image corresponding to each respiratory phase is generated from the original CT image by deformation according to the motion vector maps, and as the final step, attenuation correction using these CT images and reconstruction are performed. The effectiveness of the proposed method was evaluated using 4D-NCAT phantoms, and good stability of the voxel values near the diaphragm was observed. (author)

Gamma-ray attenuation to measure water contents and/or bulk densities of porous materials

International Nuclear Information System (INIS)

Ferraz, E.S.B.

1983-01-01

Attenuation of gamma radiation during transmission through soil and porous materials has been used for approximately three decades as a method for determining volumetric water content, theta, and bulk density, rho. This method is particularly suited for laboratory determinations of theta and rho in soil columns but it also has been used with success under field conditions. Measurements of attentuation of a collimated beam of monoernergetic gamma-rays has been used successfully by many investigators to provide rapid, non-destructive determinations for small volumes of soil. For stable soils, i.e. soils which do not swell upon wetting or shrink upon drying, rho may be assumed to remain constant during water flow through the soil, and thus changes in intensity or transmitted radiation may be attributed to changes in water content, theta. However, for unstable soils, the dry bulk density is subject to change with time during water flow through the soil and cannot be assumed to be a constant. Several investigators have utilized either a single beam of dual-energy gamma photons or two separate monoenergetic photon beams with greatly different energies to simultaneously determine theta and rho in these soils. A general review of gamma-ray attenuation methods for determining theta and rho in laboratory soil cores and in field soil profiles is reported in this paper. Theoretical equations for transmission and attenuation of gamma radiation in soils are presented for both single and double beams of gamma photons. Sensitivity, precision, accuracy, and experimental errors for the method are evaluated and discussed with respect to the theory. (author)

Attenuation of neutrons and gamma-rays in homogeneous and multilayered shields

International Nuclear Information System (INIS)

Abdo, A.E.; Megahid, R.M.

1997-01-01

Measurements were carried-out to compare the attenuation properties of homogeneous shields and shields of two layers and three layers for fast neutrons and total gamma-rays. These were performed by measuring the fast neutron and total gamma-ray spectra behind homogeneous shields of magnetite-limonite, ilmenite-ilmenite and magnetite-magnetite concretes. The two layers assembly consists of iron and one of the above mentioned concretes, while the three layers shield consists of water, iron and one of the previously mentioned concretes. All measurements were carried-out using a neutron-gamma spectrometer with stilbene scintillator coupled to a fast photo multi player tube. Separation between pulses of recoil protons and recoil electrons was achieved by a pulse shape discrimination technique. 3 tabs., 10 figs., 13 refs

Anomalies of ultrasound attenuation in metals under hydrostatic pressure

International Nuclear Information System (INIS)

Galkin, A.A.; Datsko, O.I.; Varyukhin, V.N.; Pilipenko, N.P.

1978-01-01

Ultrasonic attenuation was measured in polycrystal specimens of molybdenum, chromium and zinc under hydrostatic pressure up to 6 kbar. On the plot of ultrasound attenuation dependence on the pressure in molybdenum the maxima are observed under the pressure of 2 kbar. The anomaly of ultrasound attenuation is shown to connect only with brittle-ductile transtion

Interfacial area measurement in two-phase bubbly flows - 3. Part - comparison between the light attenuation technique and a local method

International Nuclear Information System (INIS)

Veteau, Jean-Michel; Charlot, Roland.

1981-09-01

Initially designed for rectangular test sections the light attenuation technique is reconsidered for an application in circular tubes. Principles of a two-head local probe method are discussed, including the problems related to the measurement of interface velocities. The two techniques are compared experimentally and results lead to the conclusion that, in view of its global nature, the light attenuation method is more suitable for homogeneous two-phase flows. A new experimental set up is proposed to overcome this limitation in order to obtain local values as in the probe technique [fr

Attenuation of artifacts in EEG signals measured inside an MRI scanner using constrained independent component analysis

International Nuclear Information System (INIS)

Rasheed, Tahir; Lee, Young-Koo; Lee, Soo Yeol; Kim, Tae-Seong

2009-01-01

Integration of electroencephalography (EEG) and functional magnetic imaging (fMRI) resonance will allow analysis of the brain activities at superior temporal and spatial resolution. However simultaneous acquisition of EEG and fMRI is hindered by the enhancement of artifacts in EEG, the most prominent of which are ballistocardiogram (BCG) and electro-oculogram (EOG) artifacts. The situation gets even worse if the evoked potentials are measured inside MRI for their minute responses in comparison to the spontaneous brain responses. In this study, we propose a new method of attenuating these artifacts from the spontaneous and evoked EEG data acquired inside an MRI scanner using constrained independent component analysis with a priori information about the artifacts as constraints. With the proposed techniques of reference function generation for the BCG and EOG artifacts as constraints, our new approach performs significantly better than the averaged artifact subtraction (AAS) method. The proposed method could be an alternative to the conventional ICA method for artifact attenuation, with some advantages. As a performance measure we have achieved much improved normalized power spectrum ratios (INPS) for continuous EEG and correlation coefficient (cc) values with outside MRI visual evoked potentials for visual evoked EEG, as compared to those obtained with the AAS method. The results show that our new approach is more effective than the conventional methods, almost fully automatic, and no extra ECG signal measurements are involved

A miniaturized reconfigurable broadband attenuator based on RF MEMS switches

International Nuclear Information System (INIS)

Guo, Xin; Gong, Zhuhao; Zhong, Qi; Liang, Xiaotong; Liu, Zewen

2016-01-01

Reconfigurable attenuators are widely used in microwave measurement instruments. Development of miniaturized attenuation devices with high precision and broadband performance is required for state-of-the-art applications. In this paper, a compact 3-bit microwave attenuator based on radio frequency micro-electro-mechanical system (RF MEMS) switches and polysilicon attenuation modules is presented. The device comprises 12 ohmic contact MEMS switches, π -type polysilicon resistive attenuation modules and microwave compensate structures. Special attention was paid to the design of the resistive network, compensate structures and system simulation. The device was fabricated using micromachining processes compatible with traditional integrated circuit fabrication processes. The reconfigurable attenuator integrated with RF MEMS switches and resistive attenuation modules was successfully fabricated with dimensions of 2.45  ×  4.34  ×  0.5 mm 3 , which is 1/1000th of the size of a conventional step attenuator. The measured RF performance revealed that the attenuator provides 10–70 dB attenuation at 10 dB intervals from 0.1–20 GHz with an accuracy better than  ±1.88 dB at 60 dB and an error of less than 2.22 dB at 10 dB. The return loss of each state of the 3-bit attenuator was better than 11.95 dB (VSWR  <  1.71) over the entire operating band. (paper)

Determination of mass attenuation coefficient in wood and leaves of typical trees by gamma-ray attenuation technique

International Nuclear Information System (INIS)

Miranda, Regina M. de; Pascholati, Elisabete M.

1997-01-01

Using an 241 Am source the mass attenuation coefficient of different woods and leaves of typical species of the Atlantic Forest were measured. The results for natural wood, dry wood and dry leaves indicate that the variation is very small among different species. However, woods present a higher attenuation than leaves, both depending on their water content. (author). 10 refs., 3 figs., 1 tab

Ultrasonic attenuation measurements in neutron-irradiated quartz: a microscopic model for the tunneling states

International Nuclear Information System (INIS)

Keppens, V.; Laermans, C.; Coeck, M.

1996-01-01

Ultrasonic attenuation measurements are carried out in neutron-irradiated z-cut quartz for three different doses, in a frequency range from 70 to 320 MHz. The data are analyzed using the tunneling model, and the typical TS-parameters are derived. A comparison with the results obtained from similar x-cut samples shows that the coupling of the tunneling states with the longitudinal phonons is direction-dependent. This confirms the anisotropic behaviour of the tunneling states and gives support to the microscopic picture of the TS as a rotation of coupled SiO 4 tetrahedra. (orig.)

In-situ measurement of the light attenuation in liquid argon in the GERDA cryostat

Energy Technology Data Exchange (ETDEWEB)

Schneider, Birgit [IKTP, TU Dresden (Germany); Collaboration: GERDA-Collaboration

2015-07-01

GERDA is an experiment searching for neutrinoless double beta decay in {sup 76}Ge. It uses germanium detectors which are enriched in {sup 76}Ge and operates them naked in liquid argon (LAr), which serves both as a coolant and a shield for external radiation. For phase II of GERDA it is planned to reach an exposure of 100 kg . yr with a BI of 10{sup -3} cts/(kg . yr . keV). One of the major improvements to further reduce the BI is to instrument the LAr to act as an additional background veto. The attenuation of the scintillation light in LAr creates a constraint on the effective active volume of the LAr veto and is therefore a key parameter to characterize the instrumentation. In order to measure the light attenuation in LAr, a setup was designed that could be deployed directly into the GERDA cryostat. This setup contains a movable beta source and a PMT to detect the scintillation light at different distances. The talk will describe in detail the construction of the setup, its successful deployment in the GERDA cryostat and the consecutive analysis of the acquired data.

Lifetimes in {sup 94}Zr extracted via the doppler-shift attenuation method using pγ coincidences

Energy Technology Data Exchange (ETDEWEB)

Prill, Sarah; Derya, Vera; Hennig, Andreas; Pickstone, Simon G.; Spieker, Mark; Vielmetter, Vera; Wilhelmy, Julius; Zilges, Andreas [Institute for Nuclear Physics, University of Cologne (Germany); Petkov, Pavel [Institute for Nuclear Physics, University of Cologne (Germany); INRNE, Bulgarian Academy of Sciences, Sofia (Bulgaria); National Institute for Physics and Nuclear Engineering, Bucharest (Romania)

2016-07-01

Lifetimes of excited states in {sup 94}Zr were previously measured applying the Doppler-shift attenuation method (DSAM) following the (n,n'γ) reaction.Since the two measurements were in conflict with each other, we remeasured 14 lifetimes of excited states in {sup 94}Zr in a (p,p'γ) experiment utilizing the DSAM technique. Centroid-energy shifts were extracted from proton-gated γ-ray spectra, yielding lifetime values that are independent of feeding contributions. The results were compared to the previously measured lifetimes and found to be in good agreement with the values reported, thus confirming the correction procedure introduced for the (n,n'γ) data. This contribution features our new results and introduces the (p,p'γ) DSAM technique, which is now available in Cologne.

Earth-Space Link Attenuation Estimation via Ground Radar Kdp

Science.gov (United States)

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.

Insights into the lithospheric architecture of Iberia and Morocco from teleseismic body-wave attenuation

Science.gov (United States)

Bezada, Maximiliano J.

2017-11-01

The long and often complicated tectonic history of continental lithosphere results in lateral strength heterogeneities which in turn affect the style and localization of deformation. In this study, we produce a model for the attenuation structure of Iberia and northern Morocco using a waveform-matching approach on P-wave data from teleseismic deep-focus earthquakes. We find that attenuation is correlated with zones of intraplate deformation and seismicity, but do not find a consistent relationship between attenuation and recent volcanism. The main features of our model are low to moderate Δt* in the undeformed Tertiary basins of Spain and high Δt* in areas deformed by the Alpine orogeny. Additionally, low Δt* is found in areas where the Alboran slab is thought to be attached to the Iberian and African lithosphere, and high Δt* where it has detached. These features are robust with respect to inversion parameters, and are consistent with independent data. Very mild backazimuthal dependence of the measurements and comparison with previous results suggest that the source of the attenuation is sub-crustal. In line with other recent studies, the range of Δt* we observe is much larger than can be expected from lithospheric thickness or temperature variations.

Measurement of carbon nanotube microstructure relative density by optical attenuation and observation of size-dependent variations.

Science.gov (United States)

Park, Sei Jin; Schmidt, Aaron J; Bedewy, Mostafa; Hart, A John

2013-07-21

Engineering the density of carbon nanotube (CNT) forest microstructures is vital to applications such as electrical interconnects, micro-contact probes, and thermal interface materials. For CNT forests on centimeter-scale substrates, weight and volume can be used to calculate density. However, this is not suitable for smaller samples, including individual microstructures, and moreover does not enable mapping of spatial density variations within the forest. We demonstrate that the relative mass density of individual CNT microstructures can be measured by optical attenuation, with spatial resolution equaling the size of the focused spot. For this, a custom optical setup was built to measure the transmission of a focused laser beam through CNT microstructures. The transmittance was correlated with the thickness of the CNT microstructures by Beer-Lambert-Bouguer law to calculate the attenuation coefficient. We reveal that the density of CNT microstructures grown by CVD can depend on their size, and that the overall density of arrays of microstructures is affected significantly by run-to-run process variations. Further, we use the technique to quantify the change in CNT microstructure density due to capillary densification. This is a useful and accessible metrology technique for CNTs in future microfabrication processes, and will enable direct correlation of density to important properties such as stiffness and electrical conductivity.

Chlorine signal attenuation in concrete.

Science.gov (United States)

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. Copyright © 2015 Elsevier Ltd. All rights reserved.

Lg Attenuation Modeling in the Middle East

Science.gov (United States)

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

2008-12-01

We present a broadband tomographic model of Lg attenuation in the Middle East derived from source- and site-corrected amplitudes. The study region spans from Turkey through the Arabian Peninsula and Iran to Pakistan, Afghanistan, and northwest India. Absolute amplitude measurements are made on hand-selected and carefully windowed seismograms for tens of stations and thousands of crustal earthquakes resulting in excellent coverage of the region. We have modified the standard attenuation tomography technique to more explicitly define the earthquake source expression in terms of the seismic moment. This facilitates the use of the model to predict the expected amplitudes of new events, an important consideration for earthquake hazard or explosion monitoring applications. We will discuss the updated method and implications of this parameterization. A conjugate gradient method is used to tomographically invert the amplitude dataset of over 8000 paths. We solve for Q variation, as well as site and source terms, for a wide range of frequencies ranging from 0.5 -- 10 Hz. The attenuation results have a strong correlation to tectonics. Shields have low attenuation, while tectonic regions have high attenuation, with the highest attenuation at 1 Hz found in eastern Turkey. The results also compare favorably to other studies in the region made using Lg propagation efficiency, Lg/Pg amplitude ratios and two-station methods. We tomographically invert the amplitude measurements for each frequency independently. In doing so, it appears the frequency-dependence of attenuation is not compatible with the power law representation of Q(f). This research was performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract number DE-AC52-07NA27344. This is LLNL contribution LLNL-ABS-406761.

Wall attenuation and scatter corrections for ion chambers: measurements versus calculations

Energy Technology Data Exchange (ETDEWEB)

Rogers, D W.O.; Bielajew, A F [National Research Council of Canada, Ottawa, ON (Canada). Div. of Physics

1990-08-01

In precision ion chamber dosimetry in air, wall attenuation and scatter are corrected for A{sub wall} (K{sub att} in IAEA terminology, K{sub w}{sup -1} in standards laboratory terminology). Using the EGS4 system the authors show that Monte Carlo calculated A{sub wall} factors predict relative variations in detector response with wall thickness which agree with all available experimental data within a statistical uncertainty of less than 0.1%. They calculated correction factors for use in exposure and air kerma standards are different by up to 1% from those obtained by extrapolating these same measurements. Using calculated correction factors would imply increases of 0.7-1.0% in the exposure and air kerma standards based on spherical and large diameter, large length cylindrical chambers and decreases of 0.3-0.5% for standards based on large diameter pancake chambers. (author).

Dehydroepiandrosterone Attenuates Cocaine-Seeking Behaviour Independently of Corticosterone Fluctuations.

Science.gov (United States)

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. © 2015 British Society for Neuroendocrinology.

SU-F-BRE-10: Methods to Simulate and Measure the Attenuation for Modeling a Couch Top with Rails for FFF Treatment Delivery On the Varian Edge Linac

International Nuclear Information System (INIS)

Gulam, M; Gardner, S; Zhao, B; Snyder, K; Song, K; Li, H; Gordon, J; Wen, N; Chetty, I; Kearns, W

2014-01-01

Purpose: To measure attenuation for modelling of the KVue Couchtop for 6X and 10X FFF SRS/SBRT treatment Methods: Treatment planning simulation studies were done using 6X FFF beams to estimate the dosimetric impact of KVue couchtops (including the Q-Fix IGRT [carbon fiber] and Calypso [nonconductive Kevlar material]) with a structure model obtained from a research workstation (Eclipse, advanced planning interface (API) v13). Prior to installation on the Varian Edge linac, the couchtop along with (Kevlar) rails were CT scanned with the rails at various positions. An additional scan with the couchtop 15cm above the CT table top was obtained with 20cm solid water to facilitate precised/indexed data acquisition. Measurements for attenuation were obtained for field sizes of 2, 4 and 10 cm 2 at 42 gantry angles including 6 pairs of opposing fields and other angles for oblique delivery where the beams traversed the couchtop and or rails. The delivery was fully automated with xml scripts running in developer mode. The results were then used to determine an accurate structure model for AAA (Eclipse v11) planning of IMRT and RapidArc delivery. Results: The planning simulation relative dose attenuation for oblique entry was not significantly different than the Exact IGRT or BrainLab iBeam couch except that the rails added 6% additional attenuation. The relative attenuation measurements for PA, PA (rails: inner position), oblique, oblique (rails: outer position), oblique (rails: inner position) were: −2.0%, −2.5%, −15.6%, −2.5%, −5.0% for 6X FFF and −1.4%, −1.5%, −12.2%, − 2.5%, −5.0% for 10X FFF with slight decrease in attenuation versus field size. A Couch structure model (with HU values) was developed. Calculation compared to measurement showed good agreement except for oblique (rails: outer position) where differences approached a magnitude of 6%. Conclusion: A model of the couch structures has been developed accounting for attenuation for FFF beams

Effects of attenuation map accuracy on attenuation-corrected micro-SPECT images

NARCIS (Netherlands)

Wu, C.; Gratama van Andel, H.A.; Laverman, P.; Boerman, O.C.; Beekman, F.J.

2013-01-01

Background In single-photon emission computed tomography (SPECT), attenuation of photon flux in tissue affects quantitative accuracy of reconstructed images. Attenuation maps derived from X-ray computed tomography (CT) can be employed for attenuation correction. The attenuation coefficients as well

An attenuated projector-backprojector for iterative SPECT reconstruction

International Nuclear Information System (INIS)

Gullberg, G.T.; Pelc, N.J.; Huesman, R.H.; Budinger, T.F.; Malko, J.A.

1985-01-01

A new ray-driven projector-backprojector which can easily be adapted for hardware implementation is described and simulated in software. The projector-backprojector discretely models the attenuated Radon transform of a source distributed within an attenuating medium as line integrals of discrete pixels, obtained using the standard sampling technique of averaging the emission source or attenuation distribution over small square regions. Attenuation factors are calculated for each pixel during the projection and backprojection operations instead of using precalculated values. The calculation of the factors requires a specification of the attenuation distribution, estimated either from an assumed constant distribution and an approximate body outline or from transmission measurements. The distribution of attenuation coefficients is stored in memory for efficient access during the projection and backprojection operations. The reconstruction of the source distribution is obtained by using a conjugate gradient or SIRT type iterative algorithm which requires one projection and one backprojection operation for each iteration. (author)

Characteristics of liver tissue for attenuate the gamma radiation

International Nuclear Information System (INIS)

Arcos P, A.; Rodriguez N, S.; Pinedo S, A.; Amador V, P.; Chacon R, A.; Vega C, H.R.

2005-01-01

It was determined the lineal attenuation coefficient of hepatic tissue before gamma radiation of a source of 137 Cs. When exposing organic material before X or gamma radiation fields, part of the energy of the photons is absorbed by the material, while another part crosses it without producing any effect. The quantity of energy that is absorbed is a measure of the dose that receives the material. The three main mechanisms by means of which the gamma rays interacting with the matter are: The Photoelectric Effect, the Compton dispersion and the Even production; the sum of these three processes is translated in the attenuation coefficient of the radiation. In this work we have used hepatic tissue of bovine, as substitute of the human hepatic tissue, and we have measured the lineal attenuation coefficient for photons of 0.662 MeV. Through a series of calculations we have determined the lineal attenuation coefficient for photons from 10 -3 to 10 -5 MeV and the measured coefficient was compared with the one calculated. (Author)

Immunogenicity and Safety of the HZ/su Adjuvanted Herpes Zoster Subunit Vaccine in Adults Previously Vaccinated With a Live Attenuated Herpes Zoster Vaccine.

Science.gov (United States)

Grupping, Katrijn; Campora, Laura; Douha, Martine; Heineman, Thomas C; Klein, Nicola P; Lal, Himal; Peterson, James; Vastiau, Ilse; Oostvogels, Lidia

2017-12-12

Protection against herpes zoster (HZ) induced by the live attenuated zoster vaccine Zostavax (ZVL) wanes within 3-7 years. Revaccination may renew protection. We assessed whether (re)vaccination with the adjuvanted HZ subunit vaccine candidate (HZ/su) induced comparable immune responses in previous ZVL recipients and ZVL-naive individuals (HZ-NonVac). In an open-label, multicenter study, adults ≥65 years of age, vaccinated with ZVL ≥5 years previously (HZ-PreVac), were matched to ZVL-naive adults (HZ-NonVac). Participants received 2 doses of HZ/su 2 months apart. The primary objective of noninferiority of the humoral immune response 1 month post-dose 2 was considered demonstrated if the upper limit of the 95% confidence interval (CI) of the adjusted anti-glycoprotein E geometric mean concentration (GMC) ratio of HZ-NonVac over HZ-PreVac was <1.5. HZ/su cellular immunogenicity, reactogenicity, and safety were also assessed. In 430 participants, humoral immune response to HZ/su was noninferior in HZ-PreVac compared with HZ-NonVac (adjusted GMC ratio, 1.04 [95% CI, .92-1.17]). Cellular immunogenicity, reactogenicity, and safety appeared to be comparable between groups. HZ/su was well-tolerated, with no safety concerns raised within 1 month post-dose 2. HZ/su induces a strong immune response irrespective of prior vaccination with ZVL, and may be an attractive option to revaccinate prior ZVL recipients. NCT02581410. © The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.

MicroRNA-Based Attenuation of Influenza Virus across Susceptible Hosts.

Science.gov (United States)

Waring, Barbara M; Sjaastad, Louisa E; Fiege, Jessica K; Fay, Elizabeth J; Reyes, Ismarc; Moriarity, Branden; Langlois, Ryan A

2018-01-15

Influenza A virus drives significant morbidity and mortality in humans and livestock. Annual circulation of the virus in livestock and waterfowl contributes to severe economic disruption and increases the risk of zoonotic transmission of novel strains into the human population, where there is no preexisting immunity. Seasonal vaccinations in humans help prevent infection and can reduce symptoms when infection does occur. However, current vaccination regimens available for livestock are limited in part due to safety concerns regarding reassortment/recombination with circulating strains. Therefore, inactivated vaccines are used instead of the more immunostimulatory live attenuated vaccines. MicroRNAs (miRNAs) have been used previously to generate attenuated influenza A viruses for use as a vaccine. Here, we systematically targeted individual influenza gene mRNAs using the same miRNA to determine the segment(s) that yields maximal attenuation potential. This analysis demonstrated that targeting of NP mRNA most efficiently ablates replication. We further increased the plasticity of miRNA-mediated attenuation of influenza A virus by exploiting a miRNA, miR-21, that is ubiquitously expressed across influenza-susceptible hosts. In order to construct this targeted virus, we used CRISPR/Cas9 to eliminate the universally expressed miR-21 from MDCK cells. miR-21-targeted viruses were attenuated in human, mouse, canine, and avian cells and drove protective immunity in mice. This strategy has the potential to enhance the safety of live attenuated vaccines in humans and zoonotic reservoirs. IMPORTANCE Influenza A virus circulates annually in both avian and human populations, causing significant morbidity, mortality, and economic burden. High incidence of zoonotic infections greatly increases the potential for transmission to humans, where no preexisting immunity or vaccine exists. There is a critical need for new vaccine strategies to combat emerging influenza outbreaks. Micro

Seismic wave attenuation and velocity dispersion in UAE carbonates

Science.gov (United States)

Ogunsami, Abdulwaheed Remi

Interpreting the seismic property of fluids in hydrocarbon reservoirs at low frequency scale has been a cherished goal of petroleum geophysics research for decades. Lately, there has been tremendous interest in understanding attenuation as a result of fluid flow in porous media. Although interesting, the emerging experimental and theoretical information still remain ambiguous and are practically not utilized for reasons not too obscure. Attenuation is frequency dependent and hard to measure in the laboratory at low frequency. This thesis describes and reports the results of an experimental study of low frequency attenuation and velocity dispersion on a selected carbonate reservoir samples in the United Arab Emirates (UAE). For the low frequency measurements, stress-strain method was used to measure the moduli from which the velocity is derived. Attenuation was measured as the phase difference between the applied stress and the strain. For the ultrasonic component, the pulse propagation method was employed. To study the fluid effect especially at reservoir in situ conditions, the measurements were made dry and saturated with liquid butane and brine at differential pressures of up to 5000 psi with pore pressure held constant at 500 psi. Similarly to what has been documented in the literatures for sandstone, attenuation of the bulk compressibility mode dominates the losses in these dry and somewhat partially saturated carbonate samples with butane and brine. Overall, the observed attenuation cannot be simply said to be frequency dependent within this low seismic band. While attenuation seems to be practically constant in the low frequency band for sample 3H, such conclusion cannot be made for sample 7H. For the velocities, significant dispersion is observed and Gassmann generally fails to match the measured velocities. Only the squirt model fairly fits the velocities, but not at all pressures. Although the observed dispersion is larger than Biot's prediction, the fact

Inhomogeneity of neutron and gamma-ray attenuation in biological shields

Energy Technology Data Exchange (ETDEWEB)

El-bakkoush, F A; El-Ghobary, A M; Megahid, R M [Reactor and Neutron physics Department, Nuclear Research Center, A.E.A., Cairo (Egypt)

1997-12-31

Measurements have been carried-out to investigate the attenuation properties of some materials which are used as biological shields around nuclear radiation sources. Investigation was performed by measuring the transmitted fast neutron and gamma-spectra through cylindrical samples of magnetite- limonite, steel and cellulose shields. The neutron and gamma spectra were measured by a neutron-gamma spectrometer with stilbene scintillator. Discrimination between neutron and gamma pulses was achieved by a discrimination method. The obtained results are displayed in the form of neutron and gamma spectra and attenuation relations which are used to derive the total macroscopic cross-sections for neutrons and total linear attenuation coefficients for gamma-rays. The values of neutron and gamma relaxation lengths are also derived for the investigated materials. 10 figs., 1 tabs.

Attenuation of the gamma rays in tissues

International Nuclear Information System (INIS)

Arcos P, A.; Rodriguez N, S.; Pinedo S, A.; Amador V, P.; Chacon R, A.; Vega C, H.R.

2005-01-01

The mass and lineal attenuation coefficient and of hepatic tissue, muscular, osseous and of brain before gamma rays of 10 -3 to 10 5 MeV were calculated. For the case of the osseous tissue the calculation was made for the cartilage, the cortical tissue and the bone marrow. During the calculations the elementary composition of the tissues of human origin was used. The calculations include by separate the Photoelectric effect, the Compton scattering and the Pair production, as well as the total. For to establish a comparison with the attenuation capacities, the coefficients of the water, the aluminum and the lead also were calculated. The study was complemented measuring the attenuation coefficient of hepatic tissue of bovine before gamma rays of 0.662 MeV of a source of 137 Cs. The measurement was made through of an experiment of photons transmission through samples frozen of hepatic tissue and with a Geiger-Mueller detector. (Author)

Anisotropic attenuation in rocks: Theory, modelling and lab measurements

Czech Academy of Sciences Publication Activity Database

Vavryčuk, Václav; Svitek, Tomáš; Lokajíček, Tomáš

2017-01-01

Roč. 208, č. 3 (2017), s. 1724-1739 ISSN 0956-540X R&D Projects: GA ČR(CZ) GAP210/12/1491; GA ČR(CZ) GC16-19751J; GA MŠk LH13102 Institutional support: RVO:67985530 ; RVO:67985831 Keywords : elasticity and anelasticity * body waves * seismic anisotropy * seismic attenuation Subject RIV: DC - Siesmology, Volcanology, Earth Structure; DB - Geology ; Mineralogy (GLU-S) OBOR OECD: Volcanology; Geology (GLU-S) Impact factor: 2.414, year: 2016

Cosmic-ray neutron simulations and measurements in Taiwan

International Nuclear Information System (INIS)

Chen, Wei-Lin; Jiang, Shiang-Huei; Sheu, Rong-Jiun

2014-01-01

This study used simulations of galactic cosmic ray in the atmosphere to investigate the neutron background environment in Taiwan, emphasising its altitude dependence and spectrum variation near interfaces. The calculated results were analysed and compared with two measurements. The first measurement was a mobile neutron survey from sea level up to 3275 m in altitude conducted using a car-mounted high-sensitivity neutron detector. The second was a previous measured result focusing on the changes in neutron spectra near air/ground and air/water interfaces. The attenuation length of cosmic-ray neutrons in the lower atmosphere was estimated to be 163 g cm -2 in Taiwan. Cosmic-ray neutron spectra vary with altitude and especially near interfaces. The determined spectra near the air/ground and air/water interfaces agree well with measurements for neutrons below 10 MeV. However, the high-energy portion of spectra was observed to be much higher than our previous estimation. Because high-energy neutrons contribute substantially to a dose evaluation, revising the annual sea-level effective dose from cosmic-ray neutrons at ground level in Taiwan to 35 μSv, which corresponds to a neutron flux of 5.30 x 10 -3 n cm -2 s -1 , was suggested. The cosmic-ray neutron background in Taiwan was studied using the FLUKA simulations and field measurements. A new measurement was performed using a car-mounted high-efficiency neutron detector, re-coding real-time neutron counting rates from sea level up to 3275 m. The attenuation of cosmic-ray neutrons in the lower atmosphere exhibited an effective attenuation length of 163 g cm -2 . The calculated neutron counting rates over predicted the measurements by ∼32 %, which leaded to a correction factor for the FLUKA-calculated cosmic-ray neutrons in the lower atmosphere in Taiwan. In addition, a previous measurement regarding neutron spectrum variation near the air/ground and air/water interfaces was re-evaluated. The results showed that the

Measurement of attenuation coefficients for bone, muscle, fat and water at 140, 364 and 662keV γ-ray energies

International Nuclear Information System (INIS)

Akar, A.; Baltas, H.; Cevik, U.; Korkmaz, F.; Okumusoglu, N.T.

2006-01-01

The half-value thicknesses, linear and mass attenuation coefficients of biological samples such as bone, muscle, fat and water have been measured at 140, 364 and 662keV γ-ray energies by using the ATOMLAB TM -930 medical spectrometer. The γ-rays were obtained from 99m Tc, 131 I and 137 Cs γ-ray point sources. Also theoretical calculations have been performed in order to obtain the half-value thicknesses and, mass and linear attenuation coefficients at photon energies 0.001keV-20MeV for bone, muscle and water samples. The calculated value and the experimental results of this work and the other results in literature are found to be in good agreement

Relationship between Secchi depth and the diffuse light attenuation coefficient in Danish estuaries

DEFF Research Database (Denmark)

Murray, Ciarán; Markager, Stiig

Analyis of temporal and spatial variation in the in the relationship between light attenuation and Secchi depth in Danish monitoring data There can be found timeseries of Secchi depth measurements in Danish waters which extend relatively far back in time. The Secchi depth measurement is therefore...... useful in that it allows comparison of present conditions with these older observations. An empirical inverse relationship between Secchi depth and light attenuation coefficient, Kd, has traditionally been used to estimate the light attenuation coefficient from Secchi depth measurements. However, studies...... have shown that the assumption of a constant inverse relationship between Kd and Secchi depth does not hold. The authors have analyzed measurements of Secchi depth and light attenuation from Danish monitoring data. The data used in our investigation was collected over a continuous period from 1986...

Defects and Materials Characterization by Analysis of Ultrasonic Signals. Study of a Technique to Measure Ultrasonic Attenuation

Science.gov (United States)

1985-05-01

de Ensayos No Destructivos de Control de la Calidad de los Materiales". Editado por Instituto Nacional de T6cnica AeroespaciaL...STUDY OF A TECH!4IUE TO MEASURE ULTRASONIC ATTENUATION. Carlos Valdecantos; Jos6 Miguel instituto Nacional de Tecnica Aeroespacial (INTA) Torrej6n de ...Ardoz, Madrid, SPAIN. Mayo 1985 DTIC ELECTE OCT2 I85 0SI. Final Report. 0 .. 3 Approved for public release; Distribution unlimited. " .Prepared for: AIR

Investigation of photon attenuation coefficients for marble

International Nuclear Information System (INIS)

Basyigit, C; Akkurt, I; Kilincarslan, S; Akkurt, A

2005-01-01

The total linear attenuation coefficients μ (cm -1 ) have been obtained using the XCOM program at photon energies of 1 keV to 1 GeV for six different natural marbles produced in different places in Turkey. The individual contribution of photon interaction processes to the total linear attenuation coefficients for marble has been investigated. The calculated results were also compared with the measurements. The results obtained for marble were also compared with concrete. (note)

Minocycline Attenuates Iron-Induced Brain Injury.

Science.gov (United States)

Zhao, Fan; Xi, Guohua; Liu, Wenqaun; Keep, Richard F; Hua, Ya

2016-01-01

Iron plays an important role in brain injury after intracerebral hemorrhage (ICH). Our previous study found minocycline reduces iron overload after ICH. The present study examined the effects of minocycline on the subacute brain injury induced by iron. Rats had an intracaudate injection of 50 μl of saline, iron, or iron + minocycline. All the animals were euthanized at day 3. Rat brains were used for immunohistochemistry (n = 5-6 per each group) and Western blotting assay (n = 4). Brain swelling, blood-brain barrier (BBB) disruption, and iron-handling proteins were measured. We found that intracerebral injection of iron resulted in brain swelling, BBB disruption, and brain iron-handling protein upregulation (p minocycline with iron significantly reduced iron-induced brain swelling (n = 5, p Minocycline significantly decreased albumin protein levels in the ipsilateral basal ganglia (p minocycline co-injected animals. In conclusion, the present study suggests that minocycline attenuates brain swelling and BBB disruption via an iron-chelation mechanism.

CO 2 Capture Capacity and Swelling Measurements of Liquid-like Nanoparticle Organic Hybrid Materials via Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy

KAUST Repository

Park, Youngjune; Shin, Dolly; Jang, Young Nam; Park, Ah-Hyung Alissa

2012-01-01

attenuated total reflectance (ATR) Fourier transform infrared (FT-IR) spectroscopy. Simultaneous measurements of CO 2 capture capacity and swelling behaviors of polyetheramine (Jeffamine M-2070) and its corresponding NOHMs (NOHM-I-PE2070) were reported

Shock wave attenuation in a micro-channel

Science.gov (United States)

Giordano, J.; Perrier, P.; Meister, L.; Brouillette, M.

2018-05-01

This work presents optical measurements of shock wave attenuation in a glass micro-channel. This transparent facility, with a cross section ranging from 1 mm× 150 μm to 1 mm× 500 μm, allowed for the use of high-speed schlieren videography to visualize the propagation of a shock wave within the entire micro-channel and to quantify velocity attenuation of the wave due to wall effects. In this paper, we present the experimental technique and the relevant data treatment we have used to increase the sensitivity of shock wave detection. Then, we compared our experimental results for different channel widths, lengths, and shock wave velocities with the analytical model for shock attenuation proposed by Russell (J Fluid Mech 27(2):305-314, 1967), which assumes laminar flow, and by Mirels (Attenuation in a shock tube due to unsteady-boundary-layer action, NACA Report 1333, 1957) for turbulent flow. We found that these models are inadequate to predict the observed data, owing to the presence of fully developed flow which violates the basic assumption of these models. The data are also compared with the empirical shock attenuation models proposed by Zeitoun (Phys Fluids 27(1):011701, 2015) and Deshpande and Puranik (Shock Waves 26(4):465-475, 2016), where better agreement is observed. Finally, we presented experimental data for the flow field behind the shock wave from measurements of the Mach wave angle which shows globally decreasing flow Mach numbers due to viscous wall effects.

Intercomparison of attenuation correction algorithms for single-polarized X-band radars

Science.gov (United States)

Lengfeld, K.; Berenguer, M.; Sempere Torres, D.

2018-03-01

Attenuation due to liquid water is one of the largest uncertainties in radar observations. The effects of attenuation are generally inversely proportional to the wavelength, i.e. observations from X-band radars are more affected by attenuation than those from C- or S-band systems. On the other hand, X-band radars can measure precipitation fields in higher temporal and spatial resolution and are more mobile and easier to install due to smaller antennas. A first algorithm for attenuation correction in single-polarized systems was proposed by Hitschfeld and Bordan (1954) (HB), but it gets unstable in case of small errors (e.g. in the radar calibration) and strong attenuation. Therefore, methods have been developed that restrict attenuation correction to keep the algorithm stable, using e.g. surface echoes (for space-borne radars) and mountain returns (for ground radars) as a final value (FV), or adjustment of the radar constant (C) or the coefficient α. In the absence of mountain returns, measurements from C- or S-band radars can be used to constrain the correction. All these methods are based on the statistical relation between reflectivity and specific attenuation. Another way to correct for attenuation in X-band radar observations is to use additional information from less attenuated radar systems, e.g. the ratio between X-band and C- or S-band radar measurements. Lengfeld et al. (2016) proposed such a method based isotonic regression of the ratio between X- and C-band radar observations along the radar beam. This study presents a comparison of the original HB algorithm and three algorithms based on the statistical relation between reflectivity and specific attenuation as well as two methods implementing additional information of C-band radar measurements. Their performance in two precipitation events (one mainly convective and the other one stratiform) shows that a restriction of the HB is necessary to avoid instabilities. A comparison with vertically pointing

Seismic attenuation structure beneath Nazca Plate subduction zone in southern Peru

Science.gov (United States)

Jang, H.; Kim, Y.; Clayton, R. W.

2017-12-01

We estimate seismic attenuation in terms of quality factors, QP and QS using P and S phases, respectively, beneath Nazca Plate subduction zone between 10°S and 18.5°S latitude in southern Peru. We first relocate 298 earthquakes with magnitude ranges of 4.0-6.5 and depth ranges of 20-280 km. We measure t*, which is an integrated attenuation through the seismic raypath between the regional earthquakes and stations. The measured t* are inverted to construct three-dimensional attenuation structures of southern Peru. Checkerboard test results for both QP and QS structures ensure good resolution in the slab-dip transition zone between flat and normal slab subduction down to a depth of 200 km. Both QP and QS results show higher attenuation continued down to a depth of 50 km beneath volcanic arc and also beneath the Quimsachata volcano, the northernmost young volcano, located far east of the main volcanic front. We also observe high attenuation in mantle wedge especially beneath the normal subduction region in both QP and QS (100-130 in QP and 100-125 in QS) and slightly higher QP and QS beneath the flat-subduction and slab-dip transition regions. We plan to relate measured attenuation in the mantle wedge to material properties such as viscosity to understand the subduction zone dynamics.

Indirect measure of X-rays spectra using TLDs

International Nuclear Information System (INIS)

Bonzi, E. V.; Mainardi, R. T.

2011-10-01

A methodology of indirect measure of X-rays spectra, emitted by conventional tubes, was developed recently and its feasibility verified in the first place by Monte Carlo simulations. For that case is intended to measure, by means of plastic scintillators, attenuation curves of dispersed beams previously. In this work were carried out measurements of attenuation curves with thermoluminescent dosimeters (TLD) to verify the kindness of the indirect measure method. The attenuation curve was also measured using an ionization chamber brand Capintec (model 192) with the purpose of making a comparison. The results of the attenuation curve measured with both dosimeters present a good resolution inside the statistical fluctuations and the spectral reconstruction using diverse parametric functions is carried out in a quick and simple way with excellent resolutions in the functional form. For this reconstruction method are of fundamental importance the following properties of the used dosimeter: in the first place the repetition of the measures, property that could check; in second place the precision of the measured data and lastly the dosimeter response, this is, the increase of the thermoluminescent signal before an increase of the photons flow of X-rays. This parameter is the gradient of the curve thermoluminescent signal versus the dose imparted to the dosimeter. The measures were realized with a generator of X-rays brand Kevex provided of a conventional tube with tungsten anti cathode that polarizes with high tension to a maximum value of 50 kV and current of 0.5 ma. (Author)

Attenuation correction method for single photon emission CT

Energy Technology Data Exchange (ETDEWEB)

Morozumi, Tatsuru; Nakajima, Masato [Keio Univ., Yokohama (Japan). Faculty of Science and Technology; Ogawa, Koichi; Yuta, Shinichi

1983-10-01

A correction method (Modified Correction Matrix method) is proposed to implement iterative correction by exactly measuring attenuation constant distribution in a test body, calculating a correction factor for every picture element, then multiply the image by these factors. Computer simulation for the comparison of the results showed that the proposed method was specifically more effective to an application to the test body, in which the rate of attenuation constant change is large, than the conventional correction matrix method. Since the actual measurement data always contain quantum noise, the noise was taken into account in the simulation. However, the correction effect was large even under the noise. For verifying its clinical effectiveness, the experiment using an acrylic phantom was also carried out. As the result, the recovery of image quality in the parts with small attenuation constant was remarkable as compared with the conventional method.

Attenuation measures of the BrainLAB imaging couch and validation on the treatment planning system Eclipse; Medidas de atenuacao da mesa BrainLAB imaging couch e validacao no sistema de planejamento Eclipse

Energy Technology Data Exchange (ETDEWEB)

Serante, Alexandre R., E-mail: alexandre.serante@gmail.com [Clinica de Radioterapia Inga, Nitero, RJ (Brazil); Goncalves, Joao G. [Instituto Oncologico, Juiz de Fora, MG (Brazil); Neves-Junior, Wellington F.P.; Leite, Joao Paulo S.; Haddad, Cecilia M.K. [Hospital Sirio-Libanes, Sao Paulo, SP (Brazil). Servico de Radioterapia. Sociedade Beneficente de Senhoras

2015-12-15

In this work, attenuation measurements were performed for the beams of energy 6 and 15MV for the couch table BrainLAB Imaging Couch, consisting of carbon fiber. The measurements were performed in the Linac Novalis-Tx (Varian) for 5 x 5 and 10 x 10 cm² field sizes, varying gantry positions. The measured data were compared with the values calculated with the treatment planning system Eclipse, calculated with the algorithm AAA, in order to validate the model of the couch included in your library. The highest attenuation for the field size of 10 x 10 cm² was 7,5% and 4,8% for the beams 6 and 15 MV, respectively. With the field size of 5 x 5 cm² the highest attenuation value was 8,1% and 5,3%, for the beams 6 and 15 MV, respectively. Both measured at gantry position 120 deg C. From the attenuation data measured with an ionization chamber, it was possible to modify the model of the couch in Eclipse to obtain the smallest difference between measured and predicted values by the TPS. (author)

Effect of beam-attenuation modulation on fluctuation measurements by heavy-ion beam probe

International Nuclear Information System (INIS)

Ross, D.W.; Sloan, M.L.; Wootton, A.J.

1991-03-01

Beam-attenuation modulation arising from density fluctuations along the orbit of the heavy-ion beam probe can distort the local amplitude, coherence, and phase derived from one- and two-point correlation measurements. Path-integral expressions for these effects are derived and applications to TEXT data are discussed. The effects depend critically on the ratio of the average fluctuation amplitude, n e , along the beam path to the local n e at the sample volume. Because the fluctuation amplitude is small in the core and rises sharply toward the plasma edge, the contamination effect is negligible in a radial zone near the edge but rises sharply to the interior of a critical radius. With increasing average plasma density, bar n e , the interior contamination increases strongly and the critical radius moves outward. 16 refs., 12 figs

The Study of Rain Specific Attenuation for the Prediction of Satellite Propagation in Malaysia

Science.gov (United States)

Mandeep, J. S.; Ng, Y. Y.; Abdullah, H.; Abdullah, M.

2010-06-01

Specific attenuation is the fundamental quantity in the calculation of rain attenuation for terrestrial path and slant paths representing as rain attenuation per unit distance (dB/km). Specific attenuation is an important element in developing the predicted rain attenuation model. This paper deals with the empirical determination of the power law coefficients which allow calculating the specific attenuation in dB/km from the knowledge of the rain rate in mm/h. The main purpose of the paper is to obtain the coefficients of k and α of power law relationship between specific attenuation. Three years (from 1st January 2006 until 31st December 2008) rain gauge and beacon data taken from USM, Nibong Tebal have been used to do the empirical procedure analysis of rain specific attenuation. The data presented are semi-empirical in nature. A year-to-year variation of the coefficients has been indicated and the empirical measured data was compared with ITU-R provided regression coefficient. The result indicated that the USM empirical measured data was significantly vary from ITU-R predicted value. Hence, ITU-R recommendation for regression coefficients of rain specific attenuation is not suitable for predicting rain attenuation at Malaysia.

Stellar Absorption Line Analysis of Local Star-forming Galaxies: The Relation between Stellar Mass, Metallicity, Dust Attenuation, and Star Formation Rate

Energy Technology Data Exchange (ETDEWEB)

Jabran Zahid, H. [Smithsonian Astrophysical Observatory, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Kudritzki, Rolf-Peter; Ho, I-Ting [University of Hawaii at Manoa, Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Conroy, Charlie [Department of Astronomy, Harvard University, Cambridge, MA, 02138 (United States); Andrews, Brett, E-mail: zahid@cfa.harvard.edu [PITT PACC, Department of Physics and Astronomy, University of Pittsburgh, 3941 O’Hara Street, Pittsburgh, PA 15260 (United States)

2017-09-20

We analyze the optical continuum of star-forming galaxies in the Sloan Digital Sky Survey by fitting stacked spectra with stellar population synthesis models to investigate the relation between stellar mass, stellar metallicity, dust attenuation, and star formation rate. We fit models calculated with star formation and chemical evolution histories that are derived empirically from multi-epoch observations of the stellar mass–star formation rate and the stellar mass–gas-phase metallicity relations, respectively. We also fit linear combinations of single-burst models with a range of metallicities and ages. Star formation and chemical evolution histories are unconstrained for these models. The stellar mass–stellar metallicity relations obtained from the two methods agree with the relation measured from individual supergiant stars in nearby galaxies. These relations are also consistent with the relation obtained from emission-line analysis of gas-phase metallicity after accounting for systematic offsets in the gas-phase metallicity. We measure dust attenuation of the stellar continuum and show that its dependence on stellar mass and star formation rate is consistent with previously reported results derived from nebular emission lines. However, stellar continuum attenuation is smaller than nebular emission line attenuation. The continuum-to-nebular attenuation ratio depends on stellar mass and is smaller in more massive galaxies. Our consistent analysis of stellar continuum and nebular emission lines paves the way for a comprehensive investigation of stellar metallicities of star-forming and quiescent galaxies.

Stellar Absorption Line Analysis of Local Star-forming Galaxies: The Relation between Stellar Mass, Metallicity, Dust Attenuation, and Star Formation Rate

International Nuclear Information System (INIS)

Jabran Zahid, H.; Kudritzki, Rolf-Peter; Ho, I-Ting; Conroy, Charlie; Andrews, Brett

2017-01-01

We analyze the optical continuum of star-forming galaxies in the Sloan Digital Sky Survey by fitting stacked spectra with stellar population synthesis models to investigate the relation between stellar mass, stellar metallicity, dust attenuation, and star formation rate. We fit models calculated with star formation and chemical evolution histories that are derived empirically from multi-epoch observations of the stellar mass–star formation rate and the stellar mass–gas-phase metallicity relations, respectively. We also fit linear combinations of single-burst models with a range of metallicities and ages. Star formation and chemical evolution histories are unconstrained for these models. The stellar mass–stellar metallicity relations obtained from the two methods agree with the relation measured from individual supergiant stars in nearby galaxies. These relations are also consistent with the relation obtained from emission-line analysis of gas-phase metallicity after accounting for systematic offsets in the gas-phase metallicity. We measure dust attenuation of the stellar continuum and show that its dependence on stellar mass and star formation rate is consistent with previously reported results derived from nebular emission lines. However, stellar continuum attenuation is smaller than nebular emission line attenuation. The continuum-to-nebular attenuation ratio depends on stellar mass and is smaller in more massive galaxies. Our consistent analysis of stellar continuum and nebular emission lines paves the way for a comprehensive investigation of stellar metallicities of star-forming and quiescent galaxies.

Use of generator substitution to determine the real attenuation of informative signals in the compromising emanation

Directory of Open Access Journals (Sweden)

Alexander A. Golyakhov

2018-05-01

Full Text Available A determination of real attenuation of information signal's radiation on a way from the source to a possible location of intelligence devices is considered to be the most difficult operation while assessing information security against leakage of electromagnetic emanation. In this context the problem of automation of this kind of measurement is of great interest. It takes considerable effort and time to measure the attenuation by existing automated systems. That is why the measurements are generally taken within the limited range of frequencies only. Along with that, a spectre of a single information impulse has a leaf-structure and is solid on every frequency leaf. So electromagnetic field intensity attenuation measurement carried on the some preselected frequencies is not able to represent the complete attenuation characteristics. The measurements of attenuation in the whole informative signal spectre within the given frequency range requires a few thousand measurements, which makes the current method ineffective and time consuming. The relevant specialized automatized measurement systems of security verification has active protection system noise measurement mode, which can be used to measure the real attenuation. In this article a rather exact method of real attenuation of informative signal of video subsystem of electron-ray tube monitor measurement is described and confirmed in experiment. The measurements were made using specialized automatized system “Sigurd” and video subsystem informative signal noise generator. The described method allows a significant reduction of  the time needed for specialized investigations of security verification on electromagnetic emanation.

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

Science.gov (United States)

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.

The sound of operation and the acoustic attenuation of the Ohmeda Medical Giraffe OmniBed™.

Science.gov (United States)

Wubben, Stephanie M; Brueggeman, Paul M; Stevens, Dennis C; Helseth, Carol C; Blaschke, Kristen

2011-01-01

The neonatal intensive care unit (NICU) is an environment that provides premature and fragile infants with health provisions needed to make a complete recovery. Premature infants are often born before their auditory systems have had an opportunity to fully mature. Research has shown that the ambient acoustic environment in the NICU exceeds the maximum noise level recommended by the American Academy of Pediatrics, even after measures have been taken to decrease noise levels. The purpose of this study is to evaluate noise levels inside an Ohmeda Medical Giraffe™ OmniBed™, the natural attenuation of the incubator, and the effects of modifications on attenuation and reverberation within the Giraffe TM OmniBed™. The normal operation of the Giraffe™ OmniBed™ is 41.7 dBA which indicates a lower noise of operation than previous studies. The Giraffe™ OmniBed™ naturally attenuates 12 dBA. Leaving an access latch or portal door open causes a statistically significant (P=.001) increase in sound within the bassinet. All modifications in the no-noise and the noise conditions showed a statistically significant (P=.001) drop in L(eq) when compared to baseline.

Interfacial area measurements in two-phase bubbly flows. Pt.1. Comparison between the light attenuation technique and the photographic method

International Nuclear Information System (INIS)

Veteau, J.-M.; Charlot, Roland.

1981-02-01

In order to measure specific area by a light attenuation technique in bubbly stationnary flows, the main features of an optical design are given. This method, valid for bubble sizes between 0,5 and several millimeters, is compared with a photographic technique. The latter gives values systematically higher (15 to 25%) than the former. The measured specific areas range from 0.5 to 2 cm -1 . The multiple sources of error inherent in the photographic method are discussed [fr

Implication of seismic attenuation for gas hydrate resource characterization, Mallik, Mackenzie Delta, Canada

Science.gov (United States)

Bellefleur, G.; Riedel, M.; Brent, T.; Wright, F.; Dallimore, S. R.

2007-10-01

Wave attenuation is an important physical property of hydrate-bearing sediments that is rarely taken into account in site characterization with seismic data. We present a field example showing improved images of hydrate-bearing sediments on seismic data after compensation of attenuation effects. Compressional quality factors estimated from zero-offset Vertical Seismic Profiling data acquired at Mallik, Northwest Territories, Canada, demonstrate significant wave attenuation for hydrate-bearing sediments. These results are in agreement with previous attenuation estimates obtained from sonic logs and crosshole data at different frequency intervals. The application of an inverse Q-filter to compensate attenuation effects of permafrost and hydrate-bearing sediments improved the resolution of surface 3D seismic data and its correlation with log data, particularly for the shallowest gas hydrate interval. Compensation of the attenuation effects of the permafrost likely explains most of the improvements for the shallow gas hydrate zone. Our results show that characterization of the Mallik gas hydrates with seismic data not corrected for attenuation would tend to overestimate thicknesses and lateral extent of hydrate-bearing strata and hence, the volume of hydrates in place.

Pathogenesis of virulent and attenuated foot-and-mouth disease virus in cattle.

Science.gov (United States)

Arzt, Jonathan; Pacheco, Juan M; Stenfeldt, Carolina; Rodriguez, Luis L

2017-05-02

Understanding the mechanisms of attenuation and virulence of foot-and-mouth disease virus (FMDV) in the natural host species is critical for development of next-generation countermeasures such as live-attenuated vaccines. Functional genomics analyses of FMDV have identified few virulence factors of which the leader proteinase (L pro ) is the most thoroughly investigated. Previous work from our laboratory has characterized host factors in cattle inoculated with virulent FMDV and attenuated mutant strains with transposon insertions within L pro . In the current study, the characteristics defining virulence of FMDV in cattle were further investigated by comparing the pathogenesis of a mutant, attenuated strain (FMDV-Mut) to the parental, virulent virus from which the mutant was derived (FMDV-WT). The only difference between the two viruses was an insertion mutation in the inter-AUG region of the leader proteinase of FMDV-Mut. All cattle were infected by simulated-natural, aerosol inoculation. Both viruses were demonstrated to establish primary infection in the nasopharyngeal mucosa with subsequent dissemination to the lungs. Immunomicroscopic localization of FMDV antigens indicated that both viruses infected superficial epithelial cells of the nasopharynx and lungs. The critical differences between the two viruses were a more rapid establishment of infection by FMDV-WT and quantitatively greater virus loads in secretions and infected tissues compared to FMDV-Mut. The slower replicating FMDV-Mut established a subclinical infection that was limited to respiratory epithelial sites, whereas the faster replication of FMDV-WT facilitated establishment of viremia, systemic dissemination of infection, and clinical disease. The mutant FMDV was capable of achieving all the same early pathogenesis landmarks as FMDV-WT, but was unable to establish systemic infection. The precise mechanism of attenuation remains undetermined; but current data suggests that the impaired replication

Deconvolution based attenuation correction for time-of-flight positron emission tomography

Science.gov (United States)

Lee, Nam-Yong

2017-10-01

For an accurate quantitative reconstruction of the radioactive tracer distribution in positron emission tomography (PET), we need to take into account the attenuation of the photons by the tissues. For this purpose, we propose an attenuation correction method for the case when a direct measurement of the attenuation distribution in the tissues is not available. The proposed method can determine the attenuation factor up to a constant multiple by exploiting the consistency condition that the exact deconvolution of noise-free time-of-flight (TOF) sinogram must satisfy. Simulation studies shows that the proposed method corrects attenuation artifacts quite accurately for TOF sinograms of a wide range of temporal resolutions and noise levels, and improves the image reconstruction for TOF sinograms of higher temporal resolutions by providing more accurate attenuation correction.

Natural attenuation of herbicides

DEFF Research Database (Denmark)

Tuxen, Nina; Højberg, Anker Lajer; Broholm, Mette Martina

2002-01-01

A field injection experiment in a sandy, aerobic aquifer showed that two phenoxy acids MCPP (mecoprop) and dichlorprop were degraded within I in downgradient of the injection wells after an apparent lag period. The plume development and microbial measurements indicated that microbial growth gover....... The observations may be important for application of natural attenuation as a remedy in field scale systems....

Seismic attenuation in the African LLSVP estimated from PcS phases

Science.gov (United States)

Liu, Chujie; Grand, Stephen P.

2018-05-01

Seismic tomography models have revealed two broad regions in the lowermost mantle marked by ∼3% slower shear velocity than normal beneath the south central Pacific and southern Africa. These two regions are known as large-low-shear-velocity provinces (LLSVP). There is debate over whether the LLSVPs can be explained by purely thermal variations or whether they must be chemically distinct from normal mantle. Elastic properties alone, have been unable to distinguish the thermal from chemical interpretations. Anelastic structure, however, can help discriminate among models of the LLSVPs since intrinsic attenuation is more sensitive to temperature than to chemical variations. Here we estimate Qμ (the shear wave quality factor) in the African LLSVP using PcS waves generated from a Scotia Arc earthquake, recorded by broadband seismometers deployed in Southern Africa during the Kaapvaal experiment. The upward leg of the PcS waves sweeps from normal mantle into the African LLSVP across the array. We use the spectral ratio (SR) and instantaneous frequency matching (IFM) techniques to measure the differential attenuation (Δt*) between waves sampling the African LLSVP and the waves that sample normal lower mantle. Using both methods for estimating Δt* we find that PcS waves sampling the LLSVP are more attenuated than the waves that miss the LLSVP yielding a Δt* difference of more than 1 s. Using the Δt* measurements we estimate the average Qμ in the LLSVP to be about 110. Using a range of activation enthalpy (H*) estimates, we find an average temperature anomaly within the LLSVP ranging from +250 to +800 K. Our estimated temperature anomaly range overlaps previous isochemical geodynamic studies that explain the LLSVP as a purely thermal structure although the large uncertainties cannot rule out chemical variations as well.

Mass attenuation coefficient of chromium and manganese compounds around absorption edge.

Science.gov (United States)

Sharanabasappa; Kaginelli, S B; Kerur, B R; Anilkumar, S; Hanumaiah, B

2009-01-01

The total mass attenuation coefficient for Potassium dichromate, Potassium chromate and Manganese acetate compounds are measured at different photon energies 5.895, 6.404, 6.490, 7.058, 8.041 and 14.390 keV using Fe-55, Co-57 and 241Am source with Copper target, radioactive sources. The photon intensity is analyzed using a high resolution HPGe detector system coupled to MCA under good geometrical arrangement. The obtained values of mass attenuation coefficient values are compared with theoretical values. This study suggests that measured mass attenuation coefficient values at and near absorption edges differ from the theoretical value by about 5-28%.

Accounting for the Spatial Observation Window in the 2-D Fourier Transform Analysis of Shear Wave Attenuation.

Science.gov (United States)

Rouze, Ned C; Deng, Yufeng; Palmeri, Mark L; Nightingale, Kathryn R

2017-10-01

Recent measurements of shear wave propagation in viscoelastic materials have been analyzed by constructing the 2-D Fourier transform (2DFT) of the shear wave signal and measuring the phase velocity c(ω) and attenuation α(ω) from the peak location and full width at half-maximum (FWHM) of the 2DFT signal at discrete frequencies. However, when the shear wave is observed over a finite spatial range, the 2DFT signal is a convolution of the true signal and the observation window, and measurements using the FWHM can yield biased results. In this study, we describe a method to account for the size of the spatial observation window using a model of the 2DFT signal and a non-linear, least-squares fitting procedure to determine c(ω) and α(ω). Results from the analysis of finite-element simulation data agree with c(ω) and α(ω) calculated from the material parameters used in the simulation. Results obtained in a viscoelastic phantom indicate that the measured attenuation is independent of the observation window and agree with measurements of c(ω) and α(ω) obtained using the previously described progressive phase and exponential decay analysis. Copyright © 2017 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

Measurement Over Large Solid Angle of Low Energy Cosmic Ray Muon Flux

Science.gov (United States)

Schreiner, H. F., III; Schwitters, R. F.

2015-12-01

Recent advancements in portable muon detectors have made cosmic ray imaging practical for many diverse applications. Working muon attenuation detectors have been built at the University of Texas and are already successfully being used to image tunnels, structures, and Mayan pyramids. Most previous studies have focused on energy measurements of the cosmic ray spectrum from of 1 GeV or higher. We have performed an accurate measurement of the ultra-low energy (muon spectrum down to the acceptance level of our detector, around one hundred MeV. Measurements include angular dependence, with acceptance approaching horizontal. Measurements were made underwater using a custom enclosure in Lake Travis, Austin, TX. This measurement will allow more accurate predictions and simulations of attenuation for small (muon tomography.

Magnitude corrections for attenuation in the upper mantle

International Nuclear Information System (INIS)

Anon.

1978-01-01

Since 1969, a consistent discrepancy in seismic magnitudes of nuclear detonations at NTS compared with magnitudes of detonations elsewhere in the world has been observed. This discrepancy can be explained in terms of a relatively high seismic attenuation for compressional waves in the upper mantle beneath the NTS and in certain other locations. A correction has been developed for this attenuation based on a relationship between the velocity of compressional waves at the top of the earth's mantle (just beneath the Mohorovicic discontinuity) and the seismic attenuation further down in the upper mantle. Our new definition of body-wave magnitude includes corrections for attenuation in the upper mantle at both ends of the teleseismic body-wave path. These corrections bring the NTS oservations into line with measurements of foreign events, and enable one to make more reliable estimates of yields of underground nuclear explosions, wherever the explosion occurs

Quantitative contrast-enhanced CT attenuation evaluation of osseous metastases following chemotherapy

Energy Technology Data Exchange (ETDEWEB)

Chang, Connie Y.; Simeone, F.J.; Torriani, Martin; Bredella, Miriam A. [Massachusetts General Hospital, Division of Musculoskeletal Imaging and Intervention, Department of Radiology, Boston, MA (United States)

2017-10-15

Osseous metastases often undergo an osteoblastic healing response following chemotherapy. The purpose of our study was to demonstrate the quantitative CT changes in attenuation of osseous metastases before and after chemotherapy. Our study was IRB approved and HIPAA compliant. Our cohort consisted of 86 consecutive cancer patients with contrast-enhanced CTs before and 14 ± 2 (12-25) months after initiation of chemotherapy (60 ± 11 years, 36 males, 50 females). The average and maximum metastasis attenuations were measured in Hounsfield units (HU) by two readers. Treatment effects were assessed using paired t-tests and Fisher exact tests. Intraclass correlation coefficients (ICCs) were calculated. Patient records were reviewed to determine the patient's clinical status (worse, unchanged, or improved) at the time of follow-up CT. The distribution of lesion types was as follows: lytic (30/86, 35%), blastic (43/86, 50%), and mixed lytic-blastic (13/86, 15%). There was a significant increase in average and maximum CT attenuation of metastases following chemotherapy for all patients, which remained statistically significant when stratified by lesion type, clinical status (worsening or improving/stable), cancer type (breast, lung), and radiation therapy (P < 0.05). In a subgroup of patients whose osseous metastases decreased in average attenuation (14/86, 16%), more patients had a worse clinical status (11/14, 79%) (P = 0.02). ICC was almost perfect for average attenuation and substantial for maximum attenuation. Quantitative assessment of osseous metastatic disease using CT attenuation measurements demonstrated a statistically significant increase in attenuation more than 12 months after initiation of chemotherapy. (orig.)

Post-exercise blood flow restriction attenuates hyperemia similarly in males and females.

Science.gov (United States)

Dankel, Scott J; Mouser, J Grant; Jessee, Matthew B; Mattocks, Kevin T; Buckner, Samuel L; Loenneke, Jeremy P

2017-08-01

Our laboratory recently demonstrated that post-exercise blood flow restriction attenuated muscle hypertrophy only in females, which we hypothesized may be due to alterations in post-exercise blood flow. The aim of this study is to test our previous hypothesis that sex differences in blood flow would exist when employing the same protocol. Twenty-two untrained individuals (12 females; 10 males) performed two exercise sessions, each involving one set of elbow flexion exercise to volitional failure on the right arm. The experimental condition had blood flow restriction applied for a 3 min post-exercise period, whereas the control condition did not. Blood flow was measured using an ultrasound at the brachial artery and was taken 1 and 4 min post-exercise. This corresponded to 1 min post inflation and 1 min post deflation in the experimental condition. There were no differences in the alterations in blood flow between the control and experimental conditions when examined across sex. Increases in blood flow [mean (standard deviation)] were as follows: males 1 min [control 764 (577) %; experimental 113 (108) %], males 4 min [control 346 (313) %; experimental 449 (371) %], females 1 min [control 558 (367) %; experimental 87 (105) %], and females 4 min [control 191 (183) %; experimental 328 (223) %]. It does not appear that the sex-specific attenuation of muscle hypertrophy we observed previously can be attributed to different alterations in post-exercise blood flow. Future studies may wish to replicate our previous training study, or examine alternative mechanisms which may be sex specific.

Tamoxifen attenuates development of lithium-induced nephrogenic diabetes insipidus in rats

DEFF Research Database (Denmark)

Tingskov, Stine Julie; Hu, Shan; Frøkiær, Jorgen

2018-01-01

of aquaporin-2 (AQP2), which are essential for water reabsorption of tubular fluid in the collecting duct. Sex hormones have previously been shown to affect the regulation of AQP2, so we tested whether tamoxifen (TAM), a selective estrogen receptor modulator, would attenuate lithium-induced alterations...... on renal water homeostasis. Rats were treated for 14 days with lithium and TAM treatment was initiated one week after onset of lithium administration. Lithium treatment resulted in severe polyuria and reduced AQP2 expression, which was ameliorated by TAM. Consistent with this, TAM attenuated downregulation...... of AQP2 and increased phosphorylation of the cAMP responsive element binding protein (CREB), which induced AQP2 expression, in freshly isolated inner medullary collecting duct suspension prepared from lithium-treated rats. In conclusion, TAM attenuated dose-dependently polyuria, impaired urine...

Split Hopkinson Resonant Bar Test for Sonic-Frequency Acoustic Velocity and Attenuation Measurements of Small, Isotropic Geologic Samples

Energy Technology Data Exchange (ETDEWEB)

Nakagawa, S.

2011-04-01

Mechanical properties (seismic velocities and attenuation) of geological materials are often frequency dependent, which necessitates measurements of the properties at frequencies relevant to a problem at hand. Conventional acoustic resonant bar tests allow measuring seismic properties of rocks and sediments at sonic frequencies (several kilohertz) that are close to the frequencies employed for geophysical exploration of oil and gas resources. However, the tests require a long, slender sample, which is often difficult to obtain from the deep subsurface or from weak and fractured geological formations. In this paper, an alternative measurement technique to conventional resonant bar tests is presented. This technique uses only a small, jacketed rock or sediment core sample mediating a pair of long, metal extension bars with attached seismic source and receiver - the same geometry as the split Hopkinson pressure bar test for large-strain, dynamic impact experiments. Because of the length and mass added to the sample, the resonance frequency of the entire system can be lowered significantly, compared to the sample alone. The experiment can be conducted under elevated confining pressures up to tens of MPa and temperatures above 100 C, and concurrently with x-ray CT imaging. The described Split Hopkinson Resonant Bar (SHRB) test is applied in two steps. First, extension and torsion-mode resonance frequencies and attenuation of the entire system are measured. Next, numerical inversions for the complex Young's and shear moduli of the sample are performed. One particularly important step is the correction of the inverted Young's moduli for the effect of sample-rod interfaces. Examples of the application are given for homogeneous, isotropic polymer samples and a natural rock sample.

ASSESSING AEROBIC NATURAL ATTENUATION OF TRICHLOROETHENE AT FOUR DOE SITES

International Nuclear Information System (INIS)

Koelsch, Michael C.; Starr, Robert C.; Sorenson, Kent S. Jr.

2005-01-01

A 3-year Department of Energy Environmental Science Management Program (EMSP) project is currently investigating natural attenuation of trichloroethane (TCE) in aerobic groundwater. This presentation summarizes the results of a screening process to identify TCE plumes at DOE facilities that are suitable for assessing the rate of TCE cometabolism under aerobic conditions. In order to estimate aerobic degradation rates, plumes had to meet the following criteria: TCE must be present in aerobic groundwater, a conservative co-contaminant must be present and have approximately the same source as TCE, and the groundwater velocity must be known. A total of 127 TCE plumes were considered across 24 DOE sites. The four sites retained for the assessment were: (1) Brookhaven National Laboratory, OU III; (2) Paducah Gaseous Diffusion Plant, Northwest Plume; (3) Rocky Flats Environmental Technology Site, Industrialized Area--Southwest Plume and 903 Pad South Plume; and (4) Savannah River Site, A/M Area Plume. For each of these sites, a co-contaminant derived from the same source area as TCE was used as a nonbiodegrading tracer. The tracer determined the extent to which concentration decreases in the plume can be accounted for solely by abiotic processes such as dispersion and dilution. Any concentration decreases not accounted for by these processes must be explained by some other natural attenuation mechanism. Thus, ''half-lives'' presented herein are in addition to attenuation that occurs due to hydrologic mechanisms. This ''tracer-corrected method'' has previously been used at the DOE's Idaho National Engineering and Environmental Laboratory in conjunction with other techniques to document the occurrence of intrinsic aerobic cometabolism. Application of this method to other DOE sites is the first step to determining whether this might be a significant natural attenuation mechanism on a broader scale. Application of the tracer-corrected method to data from the Brookhaven

SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION

Energy Technology Data Exchange (ETDEWEB)

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

2002-01-01

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

Independent component analysis for cochlear implant artifacts attenuation from electrically evoked auditory steady-state response measurements

Science.gov (United States)

Deprez, Hanne; Gransier, Robin; Hofmann, Michael; van Wieringen, Astrid; Wouters, Jan; Moonen, Marc

2018-02-01

Objective. Electrically evoked auditory steady-state responses (EASSRs) are potentially useful for objective cochlear implant (CI) fitting and follow-up of the auditory maturation in infants and children with a CI. EASSRs are recorded in the electro-encephalogram (EEG) in response to electrical stimulation with continuous pulse trains, and are distorted by significant CI artifacts related to this electrical stimulation. The aim of this study is to evaluate a CI artifacts attenuation method based on independent component analysis (ICA) for three EASSR datasets. Approach. ICA has often been used to remove CI artifacts from the EEG to record transient auditory responses, such as cortical evoked auditory potentials. Independent components (ICs) corresponding to CI artifacts are then often manually identified. In this study, an ICA based CI artifacts attenuation method was developed and evaluated for EASSR measurements with varying CI artifacts and EASSR characteristics. Artifactual ICs were automatically identified based on their spectrum. Main results. For 40 Hz amplitude modulation (AM) stimulation at comfort level, in high SNR recordings, ICA succeeded in removing CI artifacts from all recording channels, without distorting the EASSR. For lower SNR recordings, with 40 Hz AM stimulation at lower levels, or 90 Hz AM stimulation, ICA either distorted the EASSR or could not remove all CI artifacts in most subjects, except for two of the seven subjects tested with low level 40 Hz AM stimulation. Noise levels were reduced after ICA was applied, and up to 29 ICs were rejected, suggesting poor ICA separation quality. Significance. We hypothesize that ICA is capable of separating CI artifacts and EASSR in case the contralateral hemisphere is EASSR dominated. For small EASSRs or large CI artifact amplitudes, ICA separation quality is insufficient to ensure complete CI artifacts attenuation without EASSR distortion.

A proposal for PET/MRI attenuation correction with μ-values measured using a fixed-position radiation source and MRI segmentation

Energy Technology Data Exchange (ETDEWEB)

Kawaguchi, Hiroshi, E-mail: kwgc@nirs.go.jp [Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Hirano, Yoshiyuki, E-mail: yhirano@nirs.go.jp [Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Yoshida, Eiji, E-mail: rush@nirs.go.jp [Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Kershaw, Jeff, E-mail: len@nirs.go.jp [Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Shiraishi, Takahiro, E-mail: tshira@nirs.go.jp [Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Suga, Mikio, E-mail: mikio.suga@faculty.chiba-u.jp [Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Graduate School of Engineering of Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Ikoma, Yoko, E-mail: ikoma@nirs.go.jp [Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Obata, Takayuki, E-mail: t_obata@nirs.go.jp [Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Ito, Hiroshi, E-mail: hito@nirs.go.jp [Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan); Yamaya, Taiga, E-mail: taiga@nirs.go.jp [Molecular Imaging Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan)

2014-01-11

Several MRI-based attenuation correction methods have been reported for PET/MRI; these methods are expected to make efficient use of high-quality anatomical MRIs and reduce the radiation dose for PET/MRI scanning. The accuracy of the attenuation map (μ-map) from an MRI depends on the accuracy of tissue segmentation and the attenuation coefficients to be assigned (μ-values). In this study, we proposed an MRI-based μ-value estimation method with a non-rotational radiation source to construct a suitable μ-map for PET/MRI. The proposed method uses an accurately segmented tissue map, the partial path length of each tissue, and detected intensities of attenuated radiation from a fixed-position (rather than a rotating) radiation source to obtain the μ-map. We estimated the partial path length from a virtual blank scan of fixed-point radiation with the same scanner geometry using the known tissue map from MRI. The μ-values of every tissue were estimated by inverting a linear relationship involving the partial path lengths and measured radioactivity intensity. Validation of the proposed method was performed by calculating a fixed- point data set based upon real a real transmission scan. The root-mean-square error between the μ-values derived from a conventional transmission scan and those obtained with our proposed method were 2.4±1.4%, 17.4±9.1% and 6.6±4.3% for brain, bone and soft tissue other than brain, respectively. Although the error estimates for bone and soft tissue are not insignificant, the method we propose is able to estimate the brain μ-value accurately and it is this factor that most strongly affects the quantitative value of PET images because of the large volumetric ratio of the brain. -- Highlights: • An MRI-derived µ-map for the attenuation correction of PET images is proposed. • Method relies on segmentation of MRI and a fixed-point source transmission scan. • Tissue segmentation reduces the number of unknown µ-values. • Method

A proposal for PET/MRI attenuation correction with μ-values measured using a fixed-position radiation source and MRI segmentation

International Nuclear Information System (INIS)

Kawaguchi, Hiroshi; Hirano, Yoshiyuki; Yoshida, Eiji; Kershaw, Jeff; Shiraishi, Takahiro; Suga, Mikio; Ikoma, Yoko; Obata, Takayuki; Ito, Hiroshi; Yamaya, Taiga

2014-01-01

Several MRI-based attenuation correction methods have been reported for PET/MRI; these methods are expected to make efficient use of high-quality anatomical MRIs and reduce the radiation dose for PET/MRI scanning. The accuracy of the attenuation map (μ-map) from an MRI depends on the accuracy of tissue segmentation and the attenuation coefficients to be assigned (μ-values). In this study, we proposed an MRI-based μ-value estimation method with a non-rotational radiation source to construct a suitable μ-map for PET/MRI. The proposed method uses an accurately segmented tissue map, the partial path length of each tissue, and detected intensities of attenuated radiation from a fixed-position (rather than a rotating) radiation source to obtain the μ-map. We estimated the partial path length from a virtual blank scan of fixed-point radiation with the same scanner geometry using the known tissue map from MRI. The μ-values of every tissue were estimated by inverting a linear relationship involving the partial path lengths and measured radioactivity intensity. Validation of the proposed method was performed by calculating a fixed- point data set based upon real a real transmission scan. The root-mean-square error between the μ-values derived from a conventional transmission scan and those obtained with our proposed method were 2.4±1.4%, 17.4±9.1% and 6.6±4.3% for brain, bone and soft tissue other than brain, respectively. Although the error estimates for bone and soft tissue are not insignificant, the method we propose is able to estimate the brain μ-value accurately and it is this factor that most strongly affects the quantitative value of PET images because of the large volumetric ratio of the brain. -- Highlights: • An MRI-derived µ-map for the attenuation correction of PET images is proposed. • Method relies on segmentation of MRI and a fixed-point source transmission scan. • Tissue segmentation reduces the number of unknown µ-values. • Method

Monitoring reinforcement corrosion and corrosion-induced cracking using non-destructive x-ray attenuation measurements

DEFF Research Database (Denmark)

Michel, Alexander; Pease, Bradley Justin; Geiker, Mette Rica

2011-01-01

To test the applicability of the x-ray attenuation method to monitor the movement of corrosion products as well as the formation and propagation of cracks in cementitious materials reinforced mortar samples were prepared and tested under accelerated corrosion conditions. It is evident from the ex...... of the corrosion products averaged through the specimen thickness. The total mass loss of steel, obtained by the x-ray attenuation method, was found to be in very good agreement with the mass loss obtained by gravimetric method as well as Faraday's law....

Attenuation of earmuffs used simultaneously with respiratory protective devices

Directory of Open Access Journals (Sweden)

Emil Kozłowski

2017-06-01

Full Text Available Background: In the work environment, apart from the noise, employees may be exposed to other harmful factors. Therefore, they wear hearing protectors and other personal protective equipment. The aim of the study was to determine whether simultaneous use of earmuffs and respiratory protective devices affects the attenuation of earmuffs. Material and Methods: The study was conducted in laboratory conditions using the subjective REAT (Real Ear Attenuation at Threshold and objective MIRE (Microphone in Real Ear methods. The REAT method was used to measure sound attenuation of earmuffs, while MIRE was used to determine changes in attenuation of earmuffs due to the use of other personal protective equipment. Results: The study showed reduction in attenuation of earmuffs due to the use of a full face mask up to 20 dB. Using a full face mask causes that attenuation of earmuffs in the low frequency range is close to zero. Reduction in attenuation due to the use of half masks for complete with particle filters (half masks is 3–15 dB. Simultaneous use of earmuffs and filtering half masks makes small changes in attenuation not exceeding 3 dB. Conclusions: The study showed that full face masks give the greatest reduction in attenuation of earmuffs. On the other hand, the least reduction is observed in the case of filtering half masks. There is a significant difference between the reduction in attenuation of earmuffs worn with half masks for complete with particle filters because they may be equipped with different kind of the head strap. Med Pr 2017;68(3:349–361

Quantitative SPECT brain imaging: Effects of attenuation and detector response

International Nuclear Information System (INIS)

Gilland, D.R.; Jaszczak, R.J.; Bowsher, J.E.; Turkington, T.G.; Liang, Z.; Greer, K.L.; Coleman, R.E.

1993-01-01

Two physical factors that substantially degrade quantitative accuracy in SPECT imaging of the brain are attenuation and detector response. In addition to the physical factors, random noise in the reconstructed image can greatly affect the quantitative measurement. The purpose of this work was to implement two reconstruction methods that compensate for attenuation and detector response, a 3D maximum likelihood-EM method (ML) and a filtered backprojection method (FB) with Metz filter and Chang attenuation compensation, and compare the methods in terms of quantitative accuracy and image noise. The methods were tested on simulated data of the 3D Hoffman brain phantom. The simulation incorporated attenuation and distance-dependent detector response. Bias and standard deviation of reconstructed voxel intensities were measured in the gray and white matter regions. The results with ML showed that in both the gray and white matter regions as the number of iterations increased, bias decreased and standard deviation increased. Similar results were observed with FB as the Metz filter power increased. In both regions, ML had smaller standard deviation than FB for a given bias. Reconstruction times for the ML method have been greatly reduced through efficient coding, limited source support, and by computing attenuation factors only along rays perpendicular to the detector

Ascorbic acid attenuates endothelial permeability triggered by cell-free hemoglobin.

Science.gov (United States)

Kuck, Jamie L; Bastarache, Julie A; Shaver, Ciara M; Fessel, Joshua P; Dikalov, Sergey I; May, James M; Ware, Lorraine B

2018-01-01

Increased endothelial permeability is central to shock and organ dysfunction in sepsis but therapeutics targeted to known mediators of increased endothelial permeability have been unsuccessful in patient studies. We previously reported that cell-free hemoglobin (CFH) is elevated in the majority of patients with sepsis and is associated with organ dysfunction, poor clinical outcomes and elevated markers of oxidant injury. Others have shown that Vitamin C (ascorbate) may have endothelial protective effects in sepsis. In this study, we tested the hypothesis that high levels of CFH, as seen in the circulation of patients with sepsis, disrupt endothelial barrier integrity. Human umbilical vein endothelial cells (HUVEC) were grown to confluence and treated with CFH with or without ascorbate. Monolayer permeability was measured by Electric Cell-substrate Impedance Sensing (ECIS) or transfer of 14 C-inulin. Viability was measured by trypan blue exclusion. Intracellular ascorbate was measured by HPLC. CFH increased permeability in a dose- and time-dependent manner with 1 mg/ml of CFH increasing inulin transfer by 50% without affecting cell viability. CFH (1 mg/ml) also caused a dramatic reduction in intracellular ascorbate in the same time frame (1.4 mM without CFH, 0.23 mM 18 h after 1 mg/ml CFH, p < 0.05). Pre-treatment of HUVECs with ascorbate attenuated CFH induced permeability. CFH increases endothelial permeability in part through depletion of intracellular ascorbate. Supplementation of ascorbate can attenuate increases in permeability mediated by CFH suggesting a possible therapeutic approach in sepsis. Copyright © 2017 Elsevier Inc. All rights reserved.

Comparison of the nucleotide sequence of wild-type hepatitis - A virus and its attenuated candidate vaccine derivative

International Nuclear Information System (INIS)

Cohen, J.I.; Rosenblum, B.; Ticehurst, J.R.; Daemer, R.; Feinstone, S.; Purcell, R.H.

1987-01-01

Development of attenuated mutants for use as vaccines is in progress for other viruses, including influenza, rotavirus, varicella-zoster, cytomegalovirus, and hepatitis-A virus (HAV). Attenuated viruses may be derived from naturally occurring mutants that infect human or nonhuman hosts. Alternatively, attenuated mutants may be generated by passage of wild-type virus in cell culture. Production of attenuated viruses in cell culture is a laborious and empiric process. Despite previous empiric successes, understanding the molecular basis for attenuation of vaccine viruses could facilitate future development and use of live-virus vaccines. Comparison of the complete nucleotide sequences of wild-type (virulent) and vaccine (attenuated) viruses has been reported for polioviruses and yellow fever virus. Here, the authors compare the nucleotide sequence of wild-type HAV HM-175 with that of a candidate vaccine derivative

Measured surface magnetic field attenuation of shielded windows and wire mesh over an electrically small enclosure

International Nuclear Information System (INIS)

Hoeft, L.O.; Hofstra, J.S.; Karaskiewicz, R.J.; Wiser, G.

1984-01-01

The surface magnetic field attenuation of five types of shielded transparency (window) material was measured over the frequency range 10 kHz to 100 MHz by installing them on an .61 m x .61 m x .2 m enclosure, placing the enclosure on the wall of a TEM cell and measuring the surface and interior magnetic fields using a computer-controlled network analyzer system. The samples included two thicknesses of conductive grids on acrylic, hardware, cloth with 1/8 and 1/4-inch mesh, and a fine mesh laminated optical display window. These measurements are indicative of an enclosure with aperture coupling; namely, they become frequency-independent at high frequencies. Coarse mesh samples (1/8-1/4-inch mesh) were able to provide 50 to 60 dB of magnetic field reduction at tens of MHz, whereas the finer mesh did slightly better. This behavior is consistent with magnetic polarizability theory. Material thickness did not have an appreciable effect for frequencies above a MHz

Temporal Change in Coda Wave Attenuation Observed at Colima Volcano

Science.gov (United States)

DOMINGUEZ, T.; FLORES, F.; REYES, G.

2001-12-01

The last eruptive processes of Colima volcano (November 1998- January 1999) was characterized by the occurrence of several seismic swarms. During the year previous to the eruption, the seismic activity developed in such a form that we could identified several stages in the evolution of the activity. By measuring the amplitude decay of coda waves we estimated coda attenuation Qc in the frequency range 2-10 Hz. We used Sato's (1977) single scattering model for coda windows of 10 to 15 seconds beginning at twice the S-wave travel time. We found a change in Q0 of approximately a 20-30% lower toward the end of the period. We also found that Qc was frequency dependent within this range. This dependence was progressively lower until the last month of activity just before the eruption. Studies of the same type that have been carried out in other volcanoes (Fehler, et al., 1998, Londoño, 1996) showed changes in the attenuation of the seismic waves related to volcanic eruptions. Changes of coda Q can be attributed to the change of density of the open microcracks in the rocks because of the pressure generated by the pushing of magma toward the surface which is also responsible for the inflation of the volcanic edifice.

A new method for detecting hemoglobin directly in whole blood using photon attenuation techniques

International Nuclear Information System (INIS)

Medhat, M.E.

2014-01-01

The objective of the proposed work is focused on measuring iron concentration directly in whole blood as tool for estimating hemoglobin and anemic conditions in patients across the world. The investigated method depends on theory of photon attenuation through transmission of low energy in whole blood sample. The mathematical expressions for calculating hemoglobin and iron deficit on blood using photon attenuation are derived. Calculations are carried out for estimating concentration of iron in blood samples taken from children, adults and old patients and therefore measuring their hemoglobin and iron deficit from normal values. Theoretical mass attenuation coefficient values were obtained using the XCOM program. A high-resolution gamma-ray spectrometry based on high purity germanium detector was employed to measure attenuation of strongly collimated monoenergetic gamma beam through blood samples. (author)

Tracer attenuation in groundwater

Science.gov (United States)

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.

Cement-based materials' characterization using ultrasonic attenuation

Science.gov (United States)

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

Measurement of fractional x-ray absorption for radiation attenuating surgical gloves

International Nuclear Information System (INIS)

Nagalakshmi, B.; Sawant, S.G.; Nair, C.P.R.; Joshi, V.D.

2000-01-01

It is essential to make use of lead gloves having 0.25 mm lead equivalence only for routine x-ray screening as stipulated by International Commission on Radiological Protection. Such surgical gloves which provide attenuation to the extent of one half value thickness for low energy are very useful for the present trend of special x-ray examinations which are on the increase

Fuzzy clustering-based segmented attenuation correction in whole-body PET

CERN Document Server

Zaidi, H; Boudraa, A; Slosman, DO

2001-01-01

Segmented-based attenuation correction is now a widely accepted technique to reduce noise contribution of measured attenuation correction. In this paper, we present a new method for segmenting transmission images in positron emission tomography. This reduces the noise on the correction maps while still correcting for differing attenuation coefficients of specific tissues. Based on the Fuzzy C-Means (FCM) algorithm, the method segments the PET transmission images into a given number of clusters to extract specific areas of differing attenuation such as air, the lungs and soft tissue, preceded by a median filtering procedure. The reconstructed transmission image voxels are therefore segmented into populations of uniform attenuation based on the human anatomy. The clustering procedure starts with an over-specified number of clusters followed by a merging process to group clusters with similar properties and remove some undesired substructures using anatomical knowledge. The method is unsupervised, adaptive and a...

Measurement of the X-ray mass attenuation coefficients of silver in the 5-20 keV range.

Science.gov (United States)

Islam, M Tauhidul; Tantau, Lachlan J; Rae, Nicholas A; Barnea, Zwi; Tran, Chanh Q; Chantler, Christopher T

2014-03-01

The X-ray mass attenuation coefficients of silver were measured in the energy range 5-20 keV with an accuracy of 0.01-0.2% on a relative scale down to 5.3 keV, and of 0.09-1.22% on an absolute scale to 5.0 keV. This analysis confirms that with careful choice of foil thickness and careful correction for systematics, especially including harmonic contents at lower energies, the X-ray attenuation of high-Z elements can be measured with high accuracy even at low X-ray energies (silver in the low energy range, indicating the possibility of obtaining high-accuracy X-ray absorption fine structure down to the L1 edge (3.8 keV) of silver. Comparison of results reported here with an earlier data set optimized for higher energies confirms accuracy to within one standard error of each data set collected and analysed using the principles of the X-ray extended-range technique (XERT). Comparison with theory shows a slow divergence towards lower energies in this region away from absorption edges. The methodology developed can be used for the XAFS analysis of compounds and solutions to investigate structural features, bonding and coordination chemistry.

Effectiveness of computed tomography attenuation values in characterization of pericardial effusion.

Science.gov (United States)

Çetin, Mehmet Serkan; Özcan Çetin, Elif Hande; Özdemir, Mustafa; Topaloğlu, Serkan; Aras, Dursun; Temizhan, Ahmet; Aydoğdu, Sinan

2017-04-01

The aim of this study was to evaluate the effectiveness of computed tomography (CT) attenuation values in the characterization of pericardial effusion. This study consisted of 96 patients with pericardial effusion who underwent pericardiocentesis. For further diagnostic evaluation of pericardial effusion, all the patients were assessed by thorax CT. CT attenuation values were measured from at least 5 different areas of pericardial fluid by specifying the largest region of interest. The average of these measurements was computed and considered as the CT attenuation value of the patient. The patients were classified into two groups: patients with transudative pericardial effusion and those with exudative pericardial effusion. CT attenuation values were significantly higher in patients with exudative pericardial effusion than in those with transudative pericardial effusion [14.85±10.7 Hounsfield unit (HU) vs. 1.13±4.3 HU, peffusion. In addition, a cut-off value of 6.5 HU had 71.4% sensitivity and 72.3% specificity for the prediction of cardiac tamponade. In patients with pericardial effusion, CT attenuation values seem to be correlated with the characterization parameters of the fluid and may distinguish exudative pericardial effusion from transudative pericardial effusion. This parameter was also found to be a predictor of cardiac tamponade. CT attenuation values can be a useful tool in the clinical evaluation of patients with pericardial effusion.

Measurements of attenuation lengths through concrete and iron for neutrons produced by 800-MeV proton on tantalum target at ISIS

CERN Document Server

Nunomiya, T; Wright, P; Nakamura, T; Kim, E; Kurosawa, T; Taniguchi, S; Sasaki, M; Iwase, H; Uwamino, Y; Shibata, T; Ito, S; Perry, D R

2002-01-01

A deep penetration experiment through a thick bulk shield was performed at an intense spallation neutron source facility, ISIS, of the Rutherford Appleton Laboratory (RAL), United Kingdom. ISIS is a 800 MeV-200 mu A proton accelerator facility. Neutrons are produced from a tantalum target, and are shielded with approximately 3-m thick steel and 1-m thick ordinary concrete. On top of the shield, we measured the neutron flux attenuation through concrete and iron shields, which were additionally placed up to 120-cm and 60-cm thickness, respectively, using activation detectors of graphite and bismuth. The attenuation lengths of concrete and iron for high-energy neutrons above 20 MeV were obtained from the sup 1 sup 2 C(n, 2n) sup 1 sup 1 C reaction of graphite.

Pathways of volatile migration in the crust beneath Harrat Lunayyir (Saudi Arabia) during the unrest in 2009 revealed by attenuation tomography

Science.gov (United States)

El Khrepy, Sami; Koulakov, Ivan; Al-Arifi, Nassir; Sychev, Ilya

2017-04-01

Harrat Lunayyir is a relatively young basaltic field in Saudi Arabia located at the western margin of the Arabian Peninsula. In April-June 2009, strong seismic activity and ground deformations at this site marked the activation of the magma system beneath Harrat Lunayyir. In this study, we present new three-dimensional models of the attenuation of P and S waves during the unrest in 2009 based on the analysis of t*. We measured 1658 and 3170 values of t* for P and S waves, respectively, for the same earthquakes that were previously used for travel time tomography. The resulting anomalies of the P and S wave attenuation look very similar. In the center of the study area, we observe a prominent high-attenuation pattern, which coincides with the most active seismicity at shallow depths and maximum ground deformations. This high-attenuation zone may represent a zone of accumulation and ascending of gases, which originated at depths of 5-7 km due to the decompression of ascending liquid volatiles. Based on these findings and previous tomography studies, we propose that the unrest at Harrat Lunayyir in 2009 was triggered by a sudden injection of unstable liquid volatiles from deeper magma sources. At some depths, they were transformed to gases, which caused the volume to increase, and this led to seismic activation in the areas of phase transformations. The overpressurized gases ultimately found the weakest point in the rigid basaltic cover at the junction of several tectonic faults and escaped to the surface.

Two media method for linear attenuation coefficient determination of irregular soil samples

International Nuclear Information System (INIS)

Vici, Carlos Henrique Georges

2004-01-01

In several situations of nuclear applications, the knowledge of gamma-ray linear attenuation coefficient for irregular samples is necessary, such as in soil physics and geology. This work presents the validation of a methodology for the determination of the linear attenuation coefficient (μ) of irregular shape samples, in such a way that it is not necessary to know the thickness of the considered sample. With this methodology irregular soil samples (undeformed field samples) from Londrina region, north of Parana were studied. It was employed the two media method for the μ determination. It consists of the μ determination through the measurement of a gamma-ray beam attenuation by the sample sequentially immersed in two different media, with known and appropriately chosen attenuation coefficients. For comparison, the theoretical value of μ was calculated by the product of the mass attenuation coefficient, obtained by the WinXcom code, and the measured value of the density sample. This software employs the chemical composition of the samples and supplies a table of the mass attenuation coefficients versus the photon energy. To verify the validity of the two media method, compared with the simple gamma ray transmission method, regular pome stone samples were used. With these results for the attenuation coefficients and their respective deviations, it was possible to compare the two methods. In this way we concluded that the two media method is a good tool for the determination of the linear attenuation coefficient of irregular materials, particularly in the study of soils samples. (author)

Estrogen supplementation failed to attenuate biochemical indices of neutrophil infiltration or damage in rat skeletal muscles following ischemia.

Science.gov (United States)

Tiidus, Peter M; Deller, Mirada; Bombardier, Eric; Gül, Mustafa; Liu, X Linda

2005-01-01

This study examined the effects of estrogen supplementation on markers of neutrophil infiltration and damage in skeletal muscle of rats following ischemia. Male and female gonad-intact rats, with or without 14 days of estrogen supplementation were subjected to two hours of hind-limb ischemia and sacrificed at 24, 48 or 72 hours post-ischemia. Control animals were sacrificed without ischemia. Plantaris and red and white gastrocneimus muscles were removed and assayed for myeloperoxidase (MPO), a marker of neutrophil infiltration, and glucose-6-phosphate dehydrogenase (G6PD) and beta-glucuronidase (betaGLU), as markers of muscle damage. Significant elevations of MPO, G6PD and betaGLU activities were observed at various time points post-ischemia. No systematic differences between genders were noted in any of the measures. Estrogen supplementation in both male and female animals failed to significantly attenuate post-ischemia increases in MPO, G6PD and betaGLU activities in any of the muscles studied and in some cases accentuated activities of some of these measures. Unlike previous findings following exercise in skeletal muscle, this study failed to demonstrate estrogen-induced attenuation of indices of neutrophil infiltration or damage in skeletal muscles of rats up to 72 hours following ischemia. This demonstrates that estrogen may not consistently attenuate neutrophil infiltration and that a number of variables including damage modality, tissue or estrogen level may influence this.

Estrogen supplementation failed to attenuate biochemical indices of neutrophil infiltration or damage in rat skeletal muscles following ischemia

Directory of Open Access Journals (Sweden)

PETER M TIIDUS

2005-01-01

Full Text Available This study examined the effects of estrogen supplementation on markers of neutrophil infiltration and damage in skeletal muscle of rats following ischemia. Male and female gonad-intact rats, with or without 14 days of estrogen supplementation were subjected to two hours of hind-limb ischemia and sacrificed at 24, 48 or 72 hours post-ischemia. Control animals were sacrificed without ischemia. Plantaris and red and white gastrocneimus muscles were removed and assayed for myeloperoxidase (MPO, a marker of neutrophil infiltration, and glucose-6-phosphate dehydrogenase (G6PD and ß-glucuronidase (GLU, as markers of muscle damage. Significant elevations of MPO, G6PD and GLU activities were observed at various time points post-ischemia. No systematic differences between genders were noted in any of the measures. Estrogen supplementation in both male and female animals failed to significantly attenuate post-ischemia increases in MPO, G6PD and GLU activities in any of the muscles studied and in some cases accentuated activities of some of these measures. Unlike previous findings following exercise in skeletal muscle, this study failed to demonstrate estrogen-induced attenuation of indices of neutrophil infiltration or damage in skeletal muscles of rats up to 72 hours following ischemia. This demonstrates that estrogen may not consistently attenuate neutrophil infiltration and that a number of variables including damage modality, tissue or estrogen level may influence this.

Measure of the attenuation curve of a beam of X-rays with TLD-100 dosimeters of LiF; Medicion de la curva de atenuacion de un haz de rayos X con dosimetros TLD-100 de LiF

Energy Technology Data Exchange (ETDEWEB)

Bonzi, E. V.; Mainardi, R. T. [Universidad Nacional de Cordoba, Facultad de Matematica, Astronomia y Fisica, Av. Haya de la Torre y Av. Medina Allende s/n, Ciudad Universitaria, Cordoba (Argentina); Germanier, A. [Ministerio de Ciencia y Tecnologia, Ceprocor, Unidad de Estudios Fisicos, Alvarez de Arenas 230, X5004AAP Barrio Juniors, Cordoba (Argentina); Delgado, V. [Universidad Complutense de Madrid, Departamento de Fisica Medica, Ciudad Universitaria, 28040 Madrid (Spain)

2011-10-15

The attenuation curve of a beam of X-rays represents the beam intensity in function of the attenuator thickness interposed between the source and the detector. To know with the major possible precision the attenuation curve is indispensable in procedures of spectral reconstruction. Their periodic measuring also offers valuable information on the correct operation of a tube of X-rays, diagnostic or therapy, when not have a specific detector for that activity. In this work was measured the attenuation curve of a tube of X-rays operated to 50 kV and 0.5 ma, using existent elements in any diagnostic or therapy laboratory with radiations. In the measures commercial aluminum foil was used, bent until 24 times and thermoluminescent dosimeters TLD 100 - LiF. Also, for comparison, was measured this attenuation curve with an ionization chamber brand Capintec model 192. Was determined by X-rays fluorescence the composition of the aluminium foil, since the present elements in the alloy can to affect the form of the attenuation curve. It is interesting to observe that these elements are in very low proportion (ppm) that they do not alter the attenuation capacity of the pure aluminium. Finally in a precision balance we weigh a big piece (30 cm x 100 cm) of aluminium foil and we obtained the thickness in g/c m2. It is possible to obtain attenuation curves of a beam of X-rays, with a high precision procedure and reproducibility. The use of TLD-100 dosimeters of LiF or similar makes that this activity was also quick and simple. (Author)

Attenuation of VHE Gamma Rays by the Milky Way Interstellar Radiation Field

Energy Technology Data Exchange (ETDEWEB)

Moskalenko, Igor V.; /Stanford U., HEPL; Porter, Troy A.; /Louisiana State U.; Strong, Andrew W.; /Garching, Max Planck Inst., MPE

2006-04-19

The attenuation of very high energy gamma rays by pair production on the Galactic interstellar radiation field has long been thought of as negligible. However, a new calculation of the interstellar radiation field consistent with multi-wavelength observations by DIRBE and FIRAS indicates that the energy density of the Galactic interstellar radiation field is higher, particularly in the Galactic center, than previously thought. We have made a calculation of the attenuation of very high energy gamma rays in the Galaxy using this new interstellar radiation field which takes into account its nonuniform spatial and angular distributions. We find that the maximum attenuation occurs around 100 TeV at the level of about 25% for sources located at the Galactic center, and is important for both Galactic and extragalactic sources.

Errors in MR-based attenuation correction for brain imaging with PET/MR scanners

International Nuclear Information System (INIS)

Rota Kops, Elena; Herzog, Hans

2013-01-01

Aim: Attenuation correction of PET data acquired by hybrid MR/PET scanners remains a challenge, even if several methods for brain and whole-body measurements have been developed recently. A template-based attenuation correction for brain imaging proposed by our group is easy to handle and delivers reliable attenuation maps in a short time. However, some potential error sources are analyzed in this study. We investigated the choice of template reference head among all the available data (error A), and possible skull anomalies of the specific patient, such as discontinuities due to surgery (error B). Materials and methods: An anatomical MR measurement and a 2-bed-position transmission scan covering the whole head and neck region were performed in eight normal subjects (4 females, 4 males). Error A: Taking alternatively one of the eight heads as reference, eight different templates were created by nonlinearly registering the images to the reference and calculating the average. Eight patients (4 females, 4 males; 4 with brain lesions, 4 w/o brain lesions) were measured in the Siemens BrainPET/MR scanner. The eight templates were used to generate the patients' attenuation maps required for reconstruction. ROI and VOI atlas-based comparisons were performed employing all the reconstructed images. Error B: CT-based attenuation maps of two volunteers were manipulated by manually inserting several skull lesions and filling a nasal cavity. The corresponding attenuation coefficients were substituted with the water's coefficient (0.096/cm). Results: Error A: The mean SUVs over the eight templates pairs for all eight patients and all VOIs did not differ significantly one from each other. Standard deviations up to 1.24% were found. Error B: After reconstruction of the volunteers' BrainPET data with the CT-based attenuation maps without and with skull anomalies, a VOI-atlas analysis was performed revealing very little influence of the skull lesions (less than 3%), while the filled

Errors in MR-based attenuation correction for brain imaging with PET/MR scanners

Science.gov (United States)

Rota Kops, Elena; Herzog, Hans

2013-02-01

AimAttenuation correction of PET data acquired by hybrid MR/PET scanners remains a challenge, even if several methods for brain and whole-body measurements have been developed recently. A template-based attenuation correction for brain imaging proposed by our group is easy to handle and delivers reliable attenuation maps in a short time. However, some potential error sources are analyzed in this study. We investigated the choice of template reference head among all the available data (error A), and possible skull anomalies of the specific patient, such as discontinuities due to surgery (error B). Materials and methodsAn anatomical MR measurement and a 2-bed-position transmission scan covering the whole head and neck region were performed in eight normal subjects (4 females, 4 males). Error A: Taking alternatively one of the eight heads as reference, eight different templates were created by nonlinearly registering the images to the reference and calculating the average. Eight patients (4 females, 4 males; 4 with brain lesions, 4 w/o brain lesions) were measured in the Siemens BrainPET/MR scanner. The eight templates were used to generate the patients' attenuation maps required for reconstruction. ROI and VOI atlas-based comparisons were performed employing all the reconstructed images. Error B: CT-based attenuation maps of two volunteers were manipulated by manually inserting several skull lesions and filling a nasal cavity. The corresponding attenuation coefficients were substituted with the water's coefficient (0.096/cm). ResultsError A: The mean SUVs over the eight templates pairs for all eight patients and all VOIs did not differ significantly one from each other. Standard deviations up to 1.24% were found. Error B: After reconstruction of the volunteers' BrainPET data with the CT-based attenuation maps without and with skull anomalies, a VOI-atlas analysis was performed revealing very little influence of the skull lesions (less than 3%), while the filled nasal

Ketoconazole attenuates radiation-induction of tumor necrosis factor

Energy Technology Data Exchange (ETDEWEB)

Hallahan, D.E.; Virudachalam, S.; Kufe, D.W.; Weichselbaum, R.R. [Dana Farber Cancer Institute, Boston, MA (United States)

1994-07-01

Previous work has demonstrated that inhibitors of phospholipase A2 attenuate ionizing radiation-induced arachidonic acid production, protein kinase C activation, and prevent subsequent induction of the tumor necrosis factor gene. Because arachidonic acid contributes to radiation-induced tumor necrosis factor expression, the authors analyzed the effects of agents which alter arachidonate metabolism on the regulation of this gene. Phospholipase A2 inhibitors quinicrine, bromphenyl bromide, and pentoxyfylline or the inhibitor of lipoxygenase (ketoconazole) or the inhibitor of cycloxygenase (indomethacine) were added to cell culture 1 h prior to irradiation. Radiation-induced tumor necrosis factor gene expression was attenuated by each of the phospholipase A2 inhibitors (quinicrine, bromphenylbromide, and pentoxyfylline). Furthermore, ketoconazole attenuated X ray induced tumor necrosis factor gene expression. Conversely, indomethacin enhanced tumor necrosis factor expression following irradiation. The finding that radiation-induced tumor necrosis factor gene expression was attenuated by ketoconazole suggests that the lipoxygenase pathway participates in signal transduction preceding tumor necrosis factor induction. Enhancement of tumor necrosis factor expression by indomethacin following irradiation suggests that prostaglandins produced by cyclooxygenase act as negative regulators of tumor necrosis factor expression. Inhibitors of tumor necrosis factor induction ameliorate acute and subacute sequelae of radiotherapy. The authors propose therefore, that ketoconazole may reduce acute radiation sequelae such as mucositis and esophagitis through a reduction in tumor necrosis factor induction or inhibition of phospholipase A2 in addition to its antifungal activity. 25 refs., 2 figs.

Measurement of exposure buildup factors: The influence of scattered photons on gamma-ray attenuation coefficients

Science.gov (United States)

Mann, Kulwinder Singh

2018-01-01

Scattered photon's influence on measured values of attenuation coefficients (μm, cm2g-1) for six low-Z (effective atomic number) building materials, at three photon energies has been estimated. Narrow-beam transmission geometry has been used for the measurements. Samples of commonly used engineering materials (Cements, Clay, Lime-Stone, Plaster of Paris) have been selected for the present study. Standard radioactive sources Cs137 and Co60 have been used for obtaining γ-ray energies 661.66, 1173.24 and 1332.50 keV. The optical thickness (OT) of 0.5 mfp (mean free path) has been found the optimum optical thickness (OOT) for μm-measurement in the selected energy range (661.66-1332.50 keV). The aim of this investigation is to provide neglected information regarding subsistence of scattered photons in narrow beam geometry measurements for low-Z materials. The measurements have been performed for a wide range of sample-thickness (2-26 cm) such that their OT varies between 0.2-3.5 mfp in selected energy range. A computer program (GRIC2-toolkit) has been used for various theoretical computations required in this investigation. It has been concluded that in selected energy-range, good accuracy in μm-measurement of low-Z materials can be achieved by keeping their sample's OT below 0.5 mfp. The exposure buildup factors have been measured with the help of mathematical-model developed in this investigation.

Radiation attenuation gauge with magnetically coupled source

International Nuclear Information System (INIS)

Wallace, S.A.

1978-01-01

Disclosed is a radiation attenuation gauge for measuring thickness and density of a material which includes, in combination, a source of gamma radiation contained within a housing of magnetic or ferromagnetic material, and a means for measuring the intensity of gamma radiation. The measuring means has an aperture and magnetic means disposed adjacent to the aperture for attracting and holding the housed source in position before the aperture. The material to be measured is placed between the source and the measuring means

Is visual assessment of thyroid attenuation on unenhanced CT of the chest useful for detecting hypothyroidism?

Science.gov (United States)

Maldjian, P D; Chen, T

2016-11-01

To determine if visual assessment of the attenuation of morphologically normal appearing thyroid glands on unenhanced computed tomography (CT) of the chest is useful for identifying patients with decreased thyroid function. This was a retrospective study of 765 patients who underwent both unenhanced CT of the chest and thyroid function tests performed within 1 year of the CT examination. Attenuation of the thyroid gland was visually assessed in each patient relative to the attenuation of the surrounding muscles to categorise the gland as "low attenuation" (attenuation similar to surrounding muscles) or "high attenuation" (attenuation greater than surrounding muscles). Thyroid attenuation was quantitatively measured in each case to determine the validity of the visual assessment. Results of thyroid function tests were used to classify thyroid function as hypothyroid, euthyroid, or hyperthyroid. Data were analysed to determine the relationship between visual assessment of thyroid attenuation and status of thyroid function. Thyroid glands of low attenuation were present in 4.2% (32/765) of the patients. Nearly half (47%) of the patients with low-attenuation thyroids had hypofunctioning thyroid glands. Compared to patients with high-attenuation thyroids, patients with low-attenuation thyroids were significantly more likely to have decreased thyroid function (clinical and subclinical hypothyroidism) and significantly less likely to be euthyroid (p<0.0001). Quantitative measurement of thyroid attenuation confirmed the validity of the visual assessment. Low attenuation of an otherwise normal-appearing thyroid gland on unenhanced CT of the chest is strongly associated with decreased thyroid function. Copyright © 2016 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

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

Science.gov (United States)

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.

Attenuation (1/Q) estimation in reflection seismic records

International Nuclear Information System (INIS)

Raji, Wasiu; Rietbrock, Andreas

2013-01-01

Despite its numerous potential applications, the lack of a reliable method for determining attenuation (1/Q) in seismic data is an issue when utilizing attenuation for hydrocarbon exploration. In this paper, a new method for measuring attenuation in reflection seismic data is presented. The inversion process involves two key stages: computation of the centroid frequency for the individual signal using a variable window length and fast Fourier transform; and estimation of the difference in the centroid frequency and travel time for paired incident and transmitted signals. The new method introduces a shape factor and a constant which allows several spectral shapes to be used to represent a real seismic signal without altering the mathematical model. Application of the new method to synthetic data shows that it can provide reliable estimates of Q using any of the spectral shapes commonly assumed for real seismic signals. Tested against two published methods of Q measurement, the new method shows less sensitivity to interference from noise and change of frequency bandwidth. The method is also applied to a 3D data set from the Gullfaks field, North Sea, Norway. The trace length is divided into four intervals: AB, BC, CD, and DE. Results show that interval AB has the lowest 1/Q value, and that interval BC has the highest 1/Q value. The values of 1/Q measured in the CDP stack using the new method are consistent with those measured using the classical spectral ratio method. (paper)

Towards a quantitative, measurement-based estimate of the uncertainty in photon mass attenuation coefficients at radiation therapy energies

Science.gov (United States)

Ali, E. S. M.; Spencer, B.; McEwen, M. R.; Rogers, D. W. O.

2015-02-01

In this study, a quantitative estimate is derived for the uncertainty in the XCOM photon mass attenuation coefficients in the energy range of interest to external beam radiation therapy—i.e. 100 keV (orthovoltage) to 25 MeV—using direct comparisons of experimental data against Monte Carlo models and theoretical XCOM data. Two independent datasets are used. The first dataset is from our recent transmission measurements and the corresponding EGSnrc calculations (Ali et al 2012 Med. Phys. 39 5990-6003) for 10-30 MV photon beams from the research linac at the National Research Council Canada. The attenuators are graphite and lead, with a total of 140 data points and an experimental uncertainty of ˜0.5% (k = 1). An optimum energy-independent cross section scaling factor that minimizes the discrepancies between measurements and calculations is used to deduce cross section uncertainty. The second dataset is from the aggregate of cross section measurements in the literature for graphite and lead (49 experiments, 288 data points). The dataset is compared to the sum of the XCOM data plus the IAEA photonuclear data. Again, an optimum energy-independent cross section scaling factor is used to deduce the cross section uncertainty. Using the average result from the two datasets, the energy-independent cross section uncertainty estimate is 0.5% (68% confidence) and 0.7% (95% confidence). The potential for energy-dependent errors is discussed. Photon cross section uncertainty is shown to be smaller than the current qualitative ‘envelope of uncertainty’ of the order of 1-2%, as given by Hubbell (1999 Phys. Med. Biol 44 R1-22).

Millimetre wave attenuation of prototype diagnostic components for the ITER bolometers

Energy Technology Data Exchange (ETDEWEB)

Meister, H., E-mail: meister@ipp.mpg.de [Max-Planck-Institut für Plasmaphysik, Garching (Germany); Kasparek, W. [Universität Stuttgart, Institut für Grenzflächenverfahrenstechnik & Plasmatechnologie, Stuttgart (Germany); Zhang, D.; Hirsch, M. [Max-Planck-Institut für Plasmaphysik, Teilinstitut Greifswald, Greifswald (Germany); Koll, J. [Max-Planck-Institut für Plasmaphysik, Garching (Germany); Zeitler, A. [Universität Stuttgart, Institut für Grenzflächenverfahrenstechnik & Plasmatechnologie, Stuttgart (Germany)

2015-10-15

Highlights: • Attenuation of ECRH stray radiation in ITER demonstrated for bolometer prototypes. • Collimator with microwave reflecting grid achieves >70 dB at 170 GHz (ITER frequency). • For frequencies >250 GHz (ECE radiation) ceramic coating showed 40 dB attenuation. • Good shielding at joints of components is prerequisite to prevent microwave leakage. • These methods prevent the impact of ECRH stray radiation on bolometer measurements. - Abstract: Bolometers in current and future fusion devices, in particular those in ITER, are vulnerable to stray radiation from electron cyclotron resonance heating (ECRH) which results in measurement errors for plasma radiation detection. To protect the detectors from this stray radiation in the millimetre wavelength range, dedicated diagnostic components have been designed and tested. One option is to place a top plate which contains a microwave-reflecting grid onto the collimators. Another option investigated is the coating of the collimator channels using a microwave absorbing ceramic. Measurements of the mm-wave attenuation of the collimator in front of the bolometer detectors with and without top plate or coated collimator channels have been performed in the frequency range of 125–420 GHz. The attenuation factor of the collimator channels at 170 GHz (the ECRH frequency for ITER) with neither microwave grid nor coating is typically 10 dB. The coating enhances this to 40 dB and including the microwave grid yields at least an attenuation factor of 70 dB, which is sufficient to reduce the residual ECRH induced signal significantly below the one due to plasma radiation. Placing a bolometer camera (collimator connected to detector housing) inside the isotropic microwave field of the test facility MISTRAL, the attenuation factor of the full diagnostic set-up using a top plate was determined to be in the order of 45 dB. This degraded attenuation implies that particular attention has to be paid to design and quality

Attenuation and velocity dispersion in the exploration seismic frequency band

Science.gov (United States)

Sun, Langqiu

In an anelastic medium, seismic waves are distorted by attenuation and velocity dispersion, which depend on petrophysical properties of reservoir rocks. The effective attenuation and velocity dispersion is a combination of intrinsic attenuation and apparent attenuation due to scattering, transmission response, and data acquisition system. Velocity dispersion is usually neglected in seismic data processing partly because of insufficient observations in the exploration seismic frequency band. This thesis investigates the methods of measuring velocity dispersion in the exploration seismic frequency band and interprets the velocity dispersion data in terms of petrophysical properties. Broadband, uncorrelated vibrator data are suitable for measuring velocity dispersion in the exploration seismic frequency band, and a broad bandwidth optimizes the observability of velocity dispersion. Four methods of measuring velocity dispersion in uncorrelated vibrator VSP data are investigated, which are the sliding window crosscorrelation (SWCC) method, the instantaneous phase method, the spectral decomposition method, and the cross spectrum method. Among them, the SWCC method is a new method and has satisfactory robustness, accuracy, and efficiency. Using the SWCC method, velocity dispersion is measured in the uncorrelated vibrator VSP data from three areas with different geological settings, i.e., Mallik gas hydrate zone, McArthur River uranium mines, and Outokumpu crystalline rocks. The observed velocity dispersion is fitted to a straight line with respect to log frequency for a constant (frequency-independent) Q value. This provides an alternative method for calculating Q. A constant Q value does not directly link to petrophysical properties. A modeling study is implemented for the Mallik and McArthur River data to interpret the velocity dispersion observations in terms of petrophysical properties. The detailed multi-parameter petrophysical reservoir models are built according to

Characterization of the Metrology beamline at the SOLEIL synchrotron and application to the determination of mass attenuation coefficients of Ag and Sn in the range 3.5 ≤ E ≤ 28 keV

International Nuclear Information System (INIS)

Menesguen, Y.; Lepy, M.C.

2011-01-01

This work presents the new Metrology beamline at the SOLEIL synchrotron facility and a first attempt to quantitative measurements of mass attenuation coefficients for Ag and Sn performed on the hard X-ray branch. We first describe the beamline itself and the characterization performed of the unfocused monochromatic beam running mode. We performed a first experimental measurement of mass attenuation coefficients in the range 3.5 ≤ E ≤ 28 keV and we also derived the K-absorption and L-absorption jump ratios. The results are compared with theoretical values as well as with other experimental data and agree well with previous published values. (authors)

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

Directory of Open Access Journals (Sweden)

W. J. Massman

2008-10-01

Full Text Available 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 issue at all or have only examined it superficially. Nonetheless, the attenuation of water vapor fluctuations is clearly much greater than might be expected from a passive tracer in turbulent tube flow. This study reexamines the turbulent tube flow issue for both passive and sorbing tracers with the intent of developing a physically-based semi-empirical model that describes the attenuation associated with water vapor fluctuations. Toward this end, we develop a new model of tube flow dynamics (radial profiles of the turbulent diffusivity and tube airstream velocity. We compare our new passive-tracer formulation with previous formulations in a systematic and unified way in order to assess how sensitive the passive-tracer results depend on fundamental modeling assumptions. We extend the passive tracer model to the vapor sorption/desorption case by formulating the model's wall boundary condition in terms of a physically-based semi-empirical model of the sorption/desorption vapor fluxes. Finally we synthesize all modeling and observational results into a single analytical expression that captures the effects of the mean ambient humidity and tube flow (Reynolds number on tube attenuation.

Colored Dissolved Organic Matter in Shallow Estuaries: The Effects of Source and Transport on Light Attenuation and Measurement

Science.gov (United States)

Oestreich, W. K.; Ganju, N. K.; Pohlman, J.; Suttles, S. E.

2014-12-01

Light is of great importance to the health and ecological function of shallow estuaries. Primary production in such estuaries, which is typically dominated by seagrass, is contingent upon light penetration to the deeper part of the estuarine water column. A major component contributing to light attenuation in these systems is colored dissolved organic matter (CDOM). CDOM is most often measured via a proxy, fluorescing dissolved organic matter (fDOM), due to the ease of taking rapid, accurate fDOM measurements. Fluorescence data can then be converted to absorbance by CDOM for use in light attenuation models. However, this fDOM-CDOM conversion has proven to be quite variable between estuaries, and even between sites along a given estuary. We displayed and attempted to explain this variability through the study of three diverse estuaries: West Falmouth Harbor (MA), Barnegat Bay (NJ), and Chincoteague Bay (MD/VA). Land use surrounding these estuaries ranges from wastewater treatment to agricultural operations and residential communities. Measurements of fDOM and absorbance by CDOM (quantified via spectrophotometer measurement of 0.2μm-filtered samples) were taken along a gradient from terrestrial to oceanic end-members. These measurements yielded highly variable fDOM-CDOM relationships between estuaries. The mean ratio of absorption coefficient at 340nm (m-1) to fDOM (QSU) was much higher in West Falmouth Harbor (0.874) than in Barnegat Bay (0.227) and Chincoteague Bay (0.173). This fDOM-CDOM relationship was also observed to be variable between sites within West Falmouth Harbor and Barnegat Bay, but consistent throughout sites along Chincoteague Bay. This variability, both within and between estuaries, is likely due to differing CDOM sources as a result of differences in land use in the areas surrounding these estuaries. Stable carbon isotope analysis of DOC from each site and hydrodynamic model results will be used to differentiate sources and further elucidate the

Determination of the temperature of bremsstrahlung photon generated by ultraintense laser using various thickness attenuators

International Nuclear Information System (INIS)

Hasegawa, Shuichi; Takashima, Ryuta; Todoriki, Masaru; Kikkawa, Satoshi; Soda, Keita; Takano, Kei; Oishi, Yuji; Nayuki, Takuya; Fujii, Takashi; Nemoto, Koshichi

2011-01-01

We evaluate the simplified method using the Lambert-Beer law to measure the temperature of bremsstrahlung photon generated by an ultraintense laser. Analytical values are compared to the results of the Monte Carlo calculation of GEANT4 and they agreed very well on the condition of the appropriate distance between the attenuator and the detector. We performed the experiment to measure the temperature of bremsstrahlung x-ray emitted from a metal target irradiated by a Ti:sapphire laser with 76 mJ, 72 fs, 2.2 x 10 18 W/cm 2 . For a Cu target of 30 μm thick, the photon temperature was reasonably determined to be 0.18 MeV, which is in good agreement with previous studies.

Hydrometeor Size Distribution Measurements by Imaging the Attenuation of a Laser Spot

Science.gov (United States)

Lane, John

2013-01-01

The optical extinction of a laser due to scattering of particles is a well-known phenomenon. In a laboratory environment, this physical principle is known as the Beer-Lambert law, and is often used to measure the concentration of scattering particles in a fluid or gas. This method has been experimentally shown to be a usable means to measure the dust density from a rocket plume interaction with the lunar surface. Using the same principles and experimental arrangement, this technique can be applied to hydrometeor size distributions, and for launch-pad operations, specifically as a passive hail detection and measurement system. Calibration of a hail monitoring system is a difficult process. In the past, it has required comparison to another means of measuring hydrometeor size and density. Using a technique recently developed for estimating the density of surface dust dispersed during a rocket landing, measuring the extinction of a laser passing through hail (or dust in the rocket case) yields an estimate of the second moment of the particle cloud, and hydrometeor size distribution in the terrestrial meteorological case. With the exception of disdrometers, instruments that measure rain and hail fall make indirect measurements of the drop-size distribution. Instruments that scatter microwaves off of hydrometeors, such as the WSR-88D (Weather Surveillance Radar 88 Doppler), vertical wind profilers, and microwave disdrometers, measure the sixth moment of the drop size distribution (DSD). By projecting a laser onto a target, changes in brightness of the laser spot against the target background during rain and hail yield a measurement of the DSD's second moment by way of the Beer-Lambert law. In order to detect the laser attenuation within the 8-bit resolution of most camera image arrays, a minimum path length is required. Depending on the intensity of the hail fall rate for moderate to heavy rainfall, a laser path length of 100 m is sufficient to measure variations in

Near K-edge measurement of the X-ray attenuation coefficient of heavy elements using a tuneable X-ray source based on an electron LINAC

CERN Document Server

Materna, T; Mondelaers, W; Masschaele, B

2000-01-01

The X-ray attenuation coefficients of bismuth and of uranium were measured in the regions of 40-240 and 70-240 keV, respectively, using a tuneable hard X-ray source based on the linear electron accelerator at the University of Ghent. Results were compared with the semi-empirical values of Storm and Israel and to the theoretical values of Berger and Hubbell. We also propose a simple function for the attenuation coefficient in the vicinity of the K-edge for uranium and in an extended range of energy for bismuth. The set-up of the source at Ghent is described and the future improvements are explained.

Measurement of the x-ray mass-attenuation coefficients of gold, derived quantities between 14 keV and 21 keV and determination of the bond lengths of gold

International Nuclear Information System (INIS)

Glover, J L; Chantler, C T; Barnea, Z; Rae, N A; Tran, C Q

2010-01-01

The x-ray mass-attenuation coefficients of gold are measured at 91 energies between 14 keV and 21 keV using synchrotron radiation. The measurements are accurate to between 0.08% and 0.1%. The photoelectric mass-absorption coefficients and the imaginary component of the form factors of gold are also determined. The results include the L I edge and are the most accurate and extensive gold dataset available in this energy range. An analysis of the L I edge XAFS showed excellent agreement between the measured and simulated XAFS and yielded highly accurate values of the bond lengths of gold. When our results are compared with earlier measurements and with predictions of major theoretical tabulations, significant discrepancies are noted. The comparison raises questions about the nature of discrepancies between experimental and theoretical values of mass-attenuation coefficients.

Measurement of the x-ray mass attenuation coefficient and determination of the imaginary component of the atomic form factor of molybdenum over the 13.5-41.5-keV energy range

International Nuclear Information System (INIS)

Jonge, Martin D. de; Tran, Chanh Q.; Chantler, Christopher T.; Barnea, Zwi; Dhal, Bipin B.; Cookson, David J.; Lee, Wah-Keat; Mashayekhi, Ali

2005-01-01

We use the x-ray extended-range technique (XERT) [Chantler et al., Phys. Rev. A 64, 062506 (2001)] to measure the mass attenuation coefficients of molybdenum in the x-ray energy range of 13.5-41.5 keV to 0.02-0.15 % accuracy. Measurements made over an extended range of the measurement parameter space are critically examined to identify, quantify, and correct where necessary a number of experimental systematic errors. These results represent the most extensive experimental data set for molybdenum and include absolute mass attenuation coefficients in the regions of the x-ray absorption fine structure (XAFS) and x-ray-absorption near-edge structure (XANES). The imaginary component of the atomic form-factor f 2 is derived from the photoelectric absorption after subtracting calculated Rayleigh and Compton scattering cross sections from the total attenuation. Comparison of the result with tabulations of calculated photoelectric absorption coefficients indicates that differences of 1-15 % persist between the calculated and observed values

Attenuation correction in pulmonary and myocardial single photon emission computed tomography

Energy Technology Data Exchange (ETDEWEB)

Almquist, H

2000-01-01

The objective was to develop and validate methods for single photon emission computed tomography, SPECT, allowing quantitative physiologic and diagnostic studies of lung and heart. A method for correction of variable attenuation in SPECT, based on transmission measurements before administration of an isotope to the subject, was developed and evaluated. A protocol based upon geometrically well defined phantoms was developed. In a mosaic pattern phantom count rates were corrected from 39-43% to 101-110% of reference. In healthy subjects non-gravitational pulmonary perfusion gradients observed without attenuation correctionwere artefacts caused by attenuation. Pulmonary density in centre of right lung, obtained from the transmission measurement, was 0.28 {+-} 0.03 g/ml in normal subjects. Mean density was lower in large lungs compared to smaller ones. We also showed that regional ventilation/perfusion ratios could be measured with SPECT, using the readily available tracer {sup 133}Xe. Because of the low energy of {sup 133}Xe this relies heavily upon attenuation correction. A commercially available system for attenuation correction with simultaneous emission and transmission, considered to improve myocardial SPECT, performed erroneously. This could lead to clinical misjudgement. We considered that manufacturer-independent pre-clinical tests are required. In a test of two other commercial systems, based on different principles, an adapted variant of our initial protocol was proven useful. Only one of the systems provided correct emission count rates independently on phantom configuration. Errors in the other system were related to inadequate compensation of the influence of emission activity on the transmission study.

Attenuation correction in pulmonary and myocardial single photon emission computed tomography

International Nuclear Information System (INIS)

Almquist, H.

2000-01-01

The objective was to develop and validate methods for single photon emission computed tomography, SPECT, allowing quantitative physiologic and diagnostic studies of lung and heart. A method for correction of variable attenuation in SPECT, based on transmission measurements before administration of an isotope to the subject, was developed and evaluated. A protocol based upon geometrically well defined phantoms was developed. In a mosaic pattern phantom count rates were corrected from 39-43% to 101-110% of reference. In healthy subjects non-gravitational pulmonary perfusion gradients observed without attenuation correction were artefacts caused by attenuation. Pulmonary density in centre of right lung, obtained from the transmission measurement, was 0.28 ± 0.03 g/ml in normal subjects. Mean density was lower in large lungs compared to smaller ones. We also showed that regional ventilation/perfusion ratios could be measured with SPECT, using the readily available tracer 133 Xe. Because of the low energy of 133 Xe this relies heavily upon attenuation correction. A commercially available system for attenuation correction with simultaneous emission and transmission, considered to improve myocardial SPECT, performed erroneously. This could lead to clinical misjudgement. We considered that manufacturer-independent pre-clinical tests are required. In a test of two other commercial systems, based on different principles, an adapted variant of our initial protocol was proven useful. Only one of the systems provided correct emission count rates independently on phantom configuration. Errors in the other system were related to inadequate compensation of the influence of emission activity on the transmission study

To what extent can isotopes help substantiate natural attenuation of chlorinated ethenes?

DEFF Research Database (Denmark)

Badin, A.; Broholm, Mette Martina; Hunkeler, D.

to which isotopes could help substantiate natural attenuation of chlorinated ethenes at the field scale. Our work hence aims at exploring the latter based on data acquired in 2006 in a site located in Denmark which is contaminated with PCE and its end-products TCE, cDCE, and VC. Previous work on this site...... has enabled to demonstrate that PCE and TCE were undergoing reductive dechlorination while cDCE would be at least partially degraded through reductive dechlorination1. However, the magnitude of the contaminants attenuation by biodegradation was not evaluated. Based on simple modeling including...

Attenuation and Velocity Structure in Spain and Morocco: Distinguishing Between Water, Temperature, and Partial Melt

Science.gov (United States)

Bezada, M. J.; Humphreys, E.

2014-12-01

Temperature, melt fraction, and water content affect seismic velocity and attenuation differently. Both are sensitive to temperature, but velocity is more sensitive to melt fraction and attenuation is thought to be more sensitive to water content. For these reasons, combining attenuation measurements with tomographic imaging of velocity structure can help untangle these fields and better resolve lithospheric structure and physical state. We map variations in attenuation beneath Spain and northern Morocco using teleseismic data generated by more than a dozen teleseismic deep-focus earthquakes recorded on a dense array of stations. For each event, we first estimate the source from the best quality recordings. We then apply an attenuation operator to the source estimate, using a range of t* values, to match the record at each station. We invert for a smooth map of t* from the ensemble of measurements. The spatial patterns in t* correlate very well with the tectonic domains in Spain and Morocco. In particular, areas in Spain that resisted deformation during the Variscan and Alpine orogenies produce very little attenuation. Comparing the attenuation map with seismic velocity structure we find that, in Morocco, some areas with strong low-velocity anomalies and recent volcanism do not cause high attenuation. These observations suggest that water content is a more likely cause for seismic attenuation in the study area than temperature, and that the non-attenuative low-velocity anomalies in Morocco are produced by partial mel.

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

Science.gov (United States)

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

2015-01-15

A multitude of pharmaceuticals enter surface waters via discharges of wastewater treatment plants (WWTPs), and many raise environmental and health concerns. Chemical fate models predict their concentrations using estimates of mass loading, dilution and in-stream attenuation. However, current comprehension of the attenuation rates remains a limiting factor for predictive models. We assessed in-stream attenuation of 75 pharmaceuticals in 4 river segments, aiming to characterize in-stream attenuation variability among different pharmaceutical compounds, as well as among river segments differing in environmental conditions. Our study revealed that in-stream attenuation was highly variable among pharmaceuticals and river segments and that none of the considered pharmaceutical physicochemical and molecular properties proved to be relevant in determining the mean attenuation rates. Instead, the octanol-water partition coefficient (Kow) influenced the variability of rates among river segments, likely due to its effect on sorption to sediments and suspended particles, and therefore influencing the balance between the different attenuation mechanisms (biotransformation, photolysis, sorption, and volatilization). The magnitude of the measured attenuation rates urges scientists to consider them as important as dilution when aiming to predict concentrations in freshwater ecosystems. Copyright © 2014 Elsevier B.V. All rights reserved.

Elastic Dispersion and Attenuation in Fully Saturated Sandstones: Role of Mineral Content, Porosity, and Pressures

Science.gov (United States)

Pimienta, Lucas; Borgomano, Jan V. M.; Fortin, Jérôme; Guéguen, Yves

2017-12-01

Because measuring the frequency dependence of elastic properties in the laboratory is a technical challenge, not enough experimental data exist to test the existing theories. We report measurements of three fluid-saturated sandstones over a broad frequency band: Wilkenson, Berea, and Bentheim sandstones. Those sandstones samples, chosen for their variable porosities and mineral content, are saturated by fluids of varying viscosities. The samples elastic response (Young's modulus and Poisson's ratio) and hydraulic response (fluid flow out of the sample) are measured as a function of frequency. Large dispersion and attenuation phenomena are observed over the investigated frequency range. For all samples, the variation at lowest frequency relates to a large fluid flow directly measured out of the rock samples. These are the cause (i.e., fluid flow) and consequence (i.e., dispersion/attenuation) of the transition between drained and undrained regimes. Consistently, the characteristic frequency correlates with permeability for each sandstone. Beyond this frequency, a second variation is observed for all samples, but the rocks behave differently. For Berea sandstone, an onset of dispersion/attenuation is expected from both Young's modulus and Poisson's ratio at highest frequency. For Bentheim and Wilkenson sandstones, however, only Young's modulus shows dispersion/attenuation phenomena. For Wilkenson sandstone, the viscoelastic-like dispersion/attenuation response is interpreted as squirt flow. For Bentheim sandstone, the second effect does not fully follow such response, which could be due to a lower accuracy in the measured attenuation or to the occurence of another physical effect in this rock sample.

Dust attenuation in 2 < z < 3 star-forming galaxies from deep ALMA observations of the Hubble Ultra Deep Field

Science.gov (United States)

McLure, R. J.; Dunlop, J. S.; Cullen, F.; Bourne, N.; Best, P. N.; Khochfar, S.; Bowler, R. A. A.; Biggs, A. D.; Geach, J. E.; Scott, D.; Michałowski, M. J.; Rujopakarn, W.; van Kampen, E.; Kirkpatrick, A.; Pope, A.

2018-05-01

We present the results of a new study of the relationship between infrared excess (IRX ≡ LIR/LUV), ultraviolet (UV) spectral slope (β) and stellar mass at redshifts 2 grey attenuation curve, similar to the commonly adopted Calzetti law. Based on a large, mass-complete sample of 2 ≤ z ≤ 3 star-forming galaxies drawn from multiple surveys, we proceed to derive a new empirical relationship between β and stellar mass, making it possible to predict UV attenuation (A1600) and IRX as a function of stellar mass, for any assumed attenuation law. Once again, we find that z ≃ 2.5 star-forming galaxies follow A1600-M* and IRX-M* relations consistent with a relatively grey attenuation law, and find no compelling evidence that star-forming galaxies at this epoch follow a reddening law as steep as the Small Magellanic Cloud (SMC) extinction curve. In fact, we use a simple simulation to demonstrate that previous determinations of the IRX-β relation may have been biased towards low values of IRX at red values of β, mimicking the signature expected for an SMC-like dust law. We show that this provides a plausible mechanism for reconciling apparently contradictory results in the literature and that, based on typical measurement uncertainties, stellar mass provides a cleaner prediction of UV attenuation than β. Although the situation at lower stellar masses remains uncertain, we conclude that for 2 < z < 3 star-forming galaxies with log (M_{\\ast }/M_{⊙}) ≥ 9.75, both the IRX-β and IRX-M* relations are well described by a Calzetti-like attenuation law.

Evaluation of a direct motion estimation/correction method in respiratory-gated PET/MRI with motion-adjusted attenuation.

Science.gov (United States)

Bousse, Alexandre; Manber, Richard; Holman, Beverley F; Atkinson, David; Arridge, Simon; Ourselin, Sébastien; Hutton, Brian F; Thielemans, Kris

2017-06-01

Respiratory motion compensation in PET/CT and PET/MRI is essential as motion is a source of image degradation (motion blur, attenuation artifacts). In previous work, we developed a direct method for joint image reconstruction/motion estimation (JRM) for attenuation-corrected (AC) respiratory-gated PET, which uses a single attenuation-map (μ-map). This approach was successfully implemented for respiratory-gated PET/CT, but since it relied on an accurate μ-map for motion estimation, the question of its applicability in PET/MRI is open. The purpose of this work is to investigate the feasibility of JRM in PET/MRI and to assess the robustness of the motion estimation when a degraded μ-map is used. We performed a series of JRM reconstructions from simulated PET data using a range of simulated Dixon MRI sequence derived μ-maps with wrong attenuation values in the lungs, from -100% (no attenuation) to +100% (double attenuation), as well as truncated arms. We compared the estimated motions with the one obtained from JRM in ideal conditions (no noise, true μ-map as an input). We also applied JRM on 4 patient datasets of the chest, 3 of them containing hot lesions. Patient list-mode data were gated using a principal component analysis method. We compared SUV max values of the JRM reconstructed activity images and non motion-corrected images. We also assessed the estimated motion fields by comparing the deformed JRM-reconstructed activity with individually non-AC reconstructed gates. Experiments on simulated data showed that JRM-motion estimation is robust to μ-map degradation in the sense that it produces motion fields similar to the ones obtained when using the true μ-map, regardless of the attenuation errors in the lungs (PET/MRI clinical datasets. It provides a potential alternative to existing methods where the motion fields are pre-estimated from separate MRI measurements. © 2017 University College London (UCL). Medical Physics published by Wiley Periodicals, Inc

Estimation of the self-attenuation correction factor for gamma rays emission from nuclear materials

International Nuclear Information System (INIS)

Badawy, A.; El-Gammal, W.A.

2001-01-01

This work presents an investigation of the self-attenuation of gamma-rays emission from nuclear materials (NMs) for measuring the U-235 enrichment, U-235 mass content and isotopic composition of NMs by non-destructive assay technique [NDA]. The measurements then would not need the use of suitable NM Standards which may not be available in many situations. The self-attenuation correction factor (F) may be estimated by the use of the linear attenuation factor of the assayed sample, the geometrical configuration of the assay set-up and the position of the assayed sample relative to the detector. A developed mathematical analysis makes use of specific parameters which affect the estimation of the self-attenuation of the source-detector system which emits passive gamma-rays at certain prominent signatures

Chemical effect on total mass attenuation coefficients of V, Cr, Mn, Co and Ni

International Nuclear Information System (INIS)

Soeguet, Oe.; Colak, S.; Bueyuekkasap, E.; Kuecuekoender, A.

2002-01-01

Detailed interpretation of data obtained from X-ray transmission measurements usually depends on the assumption that the contribution of each element is additive. This assumption yields the mixture rule for X-ray attenuation coefficients which is valid if molecular and chemical effects are negligible. Total mass attenuation coefficients of V, Cr, Mn, Co and Ni in various their compounds was measured. Absorption corrections were carried on data for ligands in the compounds. It was found that V, Cr, Mn, Co and Ni had different total mass attenuation coefficients in the different compounds. Results were compared with theoretical values of HUBBELL and SELTZER. (author)

Attenuation correction for SPECT

International Nuclear Information System (INIS)

Hosoba, Minoru

1986-01-01

Attenuation correction is required for the reconstruction of a quantitative SPECT image. A new method for detecting body contours, which are important for the correction of tissue attenuation, is presented. The effect of body contours, detected by the newly developed method, on the reconstructed images was evaluated using various techniques for attenuation correction. The count rates in the specified region of interest in the phantom image by the Radial Post Correction (RPC) method, the Weighted Back Projection (WBP) method, Chang's method were strongly affected by the accuracy of the contours, as compared to those by Sorenson's method. To evaluate the effect of non-uniform attenuators on the cardiac SPECT, computer simulation experiments were performed using two types of models, the uniform attenuator model (UAM) and the non-uniform attenuator model (NUAM). The RPC method showed the lowest relative percent error (%ERROR) in UAM (11 %). However, 20 to 30 percent increase in %ERROR was observed for NUAM reconstructed with the RPC, WBP, and Chang's methods. Introducing an average attenuation coefficient (0.12/cm for Tc-99m and 0.14/cm for Tl-201) in the RPC method decreased %ERROR to the levels for UAM. Finally, a comparison between images, which were obtained by 180 deg and 360 deg scans and reconstructed from the RPC method, showed that the degree of the distortion of the contour of the simulated ventricles in the 180 deg scan was 15 % higher than that in the 360 deg scan. (Namekawa, K.)

MR-based attenuation correction in brain PET based on UTE sequences

Energy Technology Data Exchange (ETDEWEB)

Cabello, Jorge; Nekolla, Stephan G; Ziegler, Sibylle I [Department of Nuclear Medicine, Klinikum rechts der Isar, Technische Universität München (Germany)

2014-07-29

Attenuation correction (AC) in brain PET/MR has recently emerged as one of the challenging tasks in the PET/MR field. It has been shown that to ignore the attenuation produced by bone can lead to errors ranging from 5-30% in regions close to bone structures. Since the information provided by the MR signal is not directly related to tissue attenuation, alternative methods have to be developed. Signal from bone tissue is difficult to measure given its short transverse relaxation time (T2). Ultrashort-echo time (UTE) pulse sequences were developed to measure signal from tissues with short T2. A combination of two consecutive UTE echoes has been used in several works to measure signal from bone tissue. The first echo is able to measure signal from bone tissue in addition to soft tissue, while the second echo contains most of the soft tissue contained in the first echo but not bone. In this work we extract the attenuation information from the difference between the logarithm of two images obtained after applying two consecutive UTE pulse sequences using the mMR scanner (Siemens Healthcare). Subsequently, image processing techniques are applied to reduce the noise and extract air cavities within the head. The resulting image is converted to linear attenuation coefficients, generating what is known as µ-map, to be used during reconstruction. For comparison purposes PET/CT scans of the same patients were acquired prior to the PET/MR scan. Additional µ-maps obtained for comparison were extracted from a Dixon sequence (used in clinical routine) and an additional µ-map calculated by the scanner based on UTE pulse sequences. Preliminary quantitative results measured in the cerebellum, using the value obtained with CT-based AC as reference, show differences of 34% without AC, 13% using the Dixon-based and UTE-based provided by the scanner, and 0.8% with the AC strategy presented here.

Mass attenuation coefficient (μ/ρ), effective atomic number (Zeff) and measurement of x-ray energy spectra using based calcium phosphate biomaterials: a comparative study

International Nuclear Information System (INIS)

Fernandes Z, M. A.; Da Silva, T. A.; Nogueira, M. S.; Goncalves Z, E.

2015-10-01

In dentistry, alveolar bone regeneration procedures using based calcium phosphate biomaterials have been shown effective. However,there are not reports in the literature of studies the interaction of low energy radiation in these biomaterials used as attenuator and not being then allowed a comparison between the theoretical values and experimental.The objective of this study was to determine the interaction of radiation parameters of four dental biomaterials - BioOss, Cerasorb M Dental, Straumann Boneceramic and Osteogen for diagnostic radiology qualities. As a material and methods, the composition of the biomaterials was determined by the analytical techniques. The samples with 0.181 cm to 0,297 cm thickness were experimentally used as attenuators for the measurement of the transmitted X-rays spectra in X-ray equipment with 50 to 90 kV range by spectrometric system comprising the Cd Te detector. After this procedure, the mass attenuation coefficient, the effective atomic number were determined and compared between all the specimens analyzed, using the program WinXCOM in the range of 10 to 200 keV. In all strains examined observed that the energy spectrum of x-rays transmitted through the BioOss has the mean energy slightly smaller than the others biomaterials for close thickness. The μ/ρ and Z eff of the biomaterials showed its dependence on photon energy and atomic number of the elements of the material analyzed. It is concluded according to the methodology employed in this study that the measurements of x-ray spectrum, μ/ρ and Z eff using biomaterials as attenuators confirmed that the thickness, density, composition of the samples, the incident photon energy are factors that determine the characteristics of radiation in a tissue or equivalent material. (Author)

Seismic Linear Noise Attenuation with Use of Radial Transform

Science.gov (United States)

Szymańska-Małysa, Żaneta

2018-03-01

One of the goals of seismic data processing is to attenuate the recorded noise in order to enable correct interpretation of the image. Radial transform has been used as a very effective tool in the attenuation of various types of linear noise, both numerical and real (such as ground roll, direct waves, head waves, guided waves etc). The result of transformation from offset - time (X - T) domain into apparent velocity - time (R - T) domain is frequency separation between reflections and linear events. In this article synthetic and real seismic shot gathers were examined. One example was targeted at far offset area of dataset where reflections and noise had similar apparent velocities and frequency bands. Another example was a result of elastic modelling where linear artefacts were produced. Bandpass filtering and scaling operation executed in radial domain attenuated all discussed types of linear noise very effectively. After noise reduction all further processing steps reveal better results, especially velocity analysis, migration and stacking. In all presented cases signal-to-noise ratio was significantly increased and reflections covered previously by noise were revealed. Power spectra of filtered seismic records preserved real dynamics of reflections.

Improved soil particle-size analysis by gamma-ray attenuation

International Nuclear Information System (INIS)

Oliveira, J.C.M.; Vaz, C.M.P.; Reichardt, K.; Swartzendruber, D.

1997-01-01

The size distribution of particles is useful for physical characterization of soil. This study was conducted to determine whether a new method of soil particle-size analysis by gamma-ray attenuation could be further improved by changing the depth and time of measurement of the suspended particle concentration during sedimentation. In addition to the advantage of nondestructive, undisturbed measurement by gamma-ray attenuation, as compared with conventional pipette or hydrometer methods, the modifications here suggested and employed do substantially decrease the total time for analysis, and will also facilitate total automation and generalize the method for other sedimentation studies. Experimental results are presented for three different Brazilian soil materials, and illustrate the nature of the fine detail provided in the cumulative particle-size distribution as given by measurements obtained during the relatively short time period of 28 min

Utilization of ilmenite/epoxy composite for neutrons and gamma rays attenuation

Energy Technology Data Exchange (ETDEWEB)

El-Sayed Abdo, A. E-mail: attiaabdo11@hotmail.com; El-Sarraf, M.A.; Gaber, F.A

2003-01-01

This work deals with the study of ilmenite/epoxy composite as an injecting mortar for cracks developed in biological concrete shields, as well as, neutrons and gamma rays attenuation. Effects of the particle size on the mechanical strengths have been studied for epoxy resin filled with crushed ilmenite with different maximum particle sizes ranging from 32 to 500 {mu}m. Thermal neutrons and gamma rays attenuation in ilmenite/epoxy composites with 75 and 80 wt.% of ilmenite concentration have been investigated. The total mass attenuation coefficients {mu}/{rho} (cm{sup 2} g{sup -1}) of gamma ray for five ilmenite/epoxy composites have been calculated using the XCOM program (version 3.1) at energies from 10 keV to 100 MeV. Also, the total mass attenuation coefficients ({mu}/{rho}) have estimated based on the measured total linear attenuation coefficients ({mu}) and compared with the calculated results where, a reasonable agreement was found.

Physical and biogeochemical controls on light attenuation in a eutrophic, back-barrier estuary

Science.gov (United States)

Ganju, Neil K.; Miselis, Jennifer L.; Aretxabaleta, Alfredo L.

2014-01-01

Light attenuation is a critical parameter governing the ecological function of shallow estuaries. In these systems primary production is often dominated by benthic macroalgae and seagrass; thus light penetration to the bed is of primary importance. We quantified light attenuation in three seagrass meadows in Barnegat Bay, New Jersey, a shallow eutrophic back-barrier estuary; two of the sites were located within designated Ecologically Sensitive Areas (ESAs). We sequentially deployed instrumentation measuring photosynthetically active radiation, chlorophyll-a (chl-a) fluorescence, dissolved organic matter fluorescence (fDOM; a proxy for colored DOM absorbance), turbidity, pressure, and water velocity at 10 min intervals over three week periods at each site. At the southernmost site, where sediment availability was highest, light attenuation was highest and dominated by turbidity and to a lesser extent chl-a and CDOM. At the central site, chl-a dominated followed by turbidity and CDOM, and at the northernmost site turbidity and CDOM contributed equally to light attenuation. At a given site, the temporal variability of light attenuation exceeded the difference in median light attenuation at the three sites, indicating the need for continuous high-temporal resolution measurements. Vessel wakes, anecdotally implicated in increasing sediment resuspension, did not contribute to local resuspension within the seagrass beds, though frequent vessel wakes were observed in the channels. With regards to light attenuation and water clarity, physical and biogeochemical variables appear to outweigh any regulation of boat traffic within the ESAs.

Numerical Study of Shock Wave Attenuation in Two-Dimensional Ducts Using Solid Obstacles: How to Utilize Shock Focusing Techniques to Attenuate Shock Waves

Directory of Open Access Journals (Sweden)

Qian Wan

2015-04-01

Full Text Available Research on shock wave mitigation in channels has been a topic of much attention in the shock wave community. One approach to attenuate an incident shock wave is to use obstacles of various geometries arranged in different patterns. This work is inspired by the study from Chaudhuri et al. (2013, in which cylinders, squares and triangles placed in staggered and non-staggered subsequent columns were used to attenuate a planar incident shock wave. Here, we present numerical simulations using a different obstacle pattern. Instead of using a matrix of obstacles, an arrangement of square or cylindrical obstacles placed along a logarithmic spiral curve is investigated, which is motivated by our previous work on shock focusing using logarithmic spirals. Results show that obstacles placed along a logarithmic spiral can delay both the transmitted and the reflected shock wave. For different incident shock Mach numbers, away from the logarithmic spiral design Mach number, this shape is effective to either delay the transmitted or the reflected shock wave. Results also confirm that the degree of attenuation depends on the obstacle shape, effective flow area and obstacle arrangement, much like other obstacle configurations.

Prediction of slant path rain attenuation statistics at various locations

Science.gov (United States)

Goldhirsh, J.

1977-01-01

The paper describes a method for predicting slant path attenuation statistics at arbitrary locations for variable frequencies and path elevation angles. The method involves the use of median reflectivity factor-height profiles measured with radar as well as the use of long-term point rain rate data and assumed or measured drop size distributions. The attenuation coefficient due to cloud liquid water in the presence of rain is also considered. Absolute probability fade distributions are compared for eight cases: Maryland (15 GHz), Texas (30 GHz), Slough, England (19 and 37 GHz), Fayetteville, North Carolina (13 and 18 GHz), and Cambridge, Massachusetts (13 and 18 GHz).

Consideration of natural attenuation. In remedation contaminated sites

Energy Technology Data Exchange (ETDEWEB)

NONE

2011-04-15

Upon the proposal submitted by ist Standing committee 5 (Contaminated Sites Committee - ALA) the Federal / State Working Group on Soil protection employed an ad hoc subcommittee dealing with considering natural attenuation in remediating contaminated sites and preparing an inter-State position paper. In the present position paper the way how to consider natural attenuation in practical remediation of contaminated sites is described. The systematic approach outlined allows an understandable decision-finding. A way is shown how the competent soil protection authorities may exercise discretion and in the framework of checking the appropriateness of measures may decide on the implementation of MNA based on a MNA concept (MNA = monitored natural attenuation). It is, however, also explained that when carrying out MNA a decision always made in an individual case is concerned which should be made in a close agreement between the obligated party and the authority.

Controlled Attenuation Parameter And Alcoholic Hepatic Steatosis

DEFF Research Database (Denmark)

Thiele, Maja; Rausch, Vanessa; Fluhr, Gabriele

2018-01-01

BACKGROUND AND AIMS: Controlled attenuation parameter (CAP) is a novel non-invasive measure of hepatic steatosis, but has not been evaluated in alcoholic liver disease. We therefore aimed to validate CAP for assessment of biopsy-verified alcoholic steatosis and to study the effect of alcohol deto...

Modeling the photochemical attenuation of down-the-drain chemicals during river transport by stochastic methods and field measurements of pharmaceuticals and personal care products.

Science.gov (United States)

Hanamoto, Seiya; Nakada, Norihide; Yamashita, Naoyuki; Tanaka, Hiroaki

2013-01-01

Existing stochastic models for predicting concentrations of down-the-drain chemicals in aquatic environments do not account for the diurnal variation of direct photolysis by sunlight, despite its being an important factor in natural attenuation. To overcome this limitation, we developed a stochastic model incorporating temporal variations in direct photolysis. To verify the model, we measured 57 pharmaceuticals and personal care products (PPCPs) in a 7.6-km stretch of an urban river, and determined their physical and biological properties in laboratory experiments. During transport along the river, 8 PPCPs, including ketoprofen and azithromycin, were attenuated by >20%, mainly owing to direct photolysis and adsorption to sediments. The photolabile PPCPs attenuated significantly in the daytime but persisted in the nighttime. The observations were similar to the values predicted by the photolysis model for the photolabile PPCPs (i.e., ketoprofen, diclofenac and furosemide) but not by the existing model. The stochastic model developed in this study was suggested to be a novel and useful stochastic model for evaluating direct photolysis of down-the-drain chemicals, which occurs during the river transport.

An empirical model of diagnostic x-ray attenuation under narrow-beam geometry

International Nuclear Information System (INIS)

Mathieu, Kelsey B.; Kappadath, S. Cheenu; White, R. Allen; Atkinson, E. Neely; Cody, Dianna D.

2011-01-01

Purpose: The purpose of this study was to develop and validate a mathematical model to describe narrow-beam attenuation of kilovoltage x-ray beams for the intended applications of half-value layer (HVL) and quarter-value layer (QVL) estimations, patient organ shielding, and computer modeling. Methods: An empirical model, which uses the Lambert W function and represents a generalized Lambert-Beer law, was developed. To validate this model, transmission of diagnostic energy x-ray beams was measured over a wide range of attenuator thicknesses [0.49-33.03 mm Al on a computed tomography (CT) scanner, 0.09-1.93 mm Al on two mammography systems, and 0.1-0.45 mm Cu and 0.49-14.87 mm Al using general radiography]. Exposure measurements were acquired under narrow-beam geometry using standard methods, including the appropriate ionization chamber, for each radiographic system. Nonlinear regression was used to find the best-fit curve of the proposed Lambert W model to each measured transmission versus attenuator thickness data set. In addition to validating the Lambert W model, we also assessed the performance of two-point Lambert W interpolation compared to traditional methods for estimating the HVL and QVL [i.e., semilogarithmic (exponential) and linear interpolation]. Results: The Lambert W model was validated for modeling attenuation versus attenuator thickness with respect to the data collected in this study (R 2 > 0.99). Furthermore, Lambert W interpolation was more accurate and less sensitive to the choice of interpolation points used to estimate the HVL and/or QVL than the traditional methods of semilogarithmic and linear interpolation. Conclusions: The proposed Lambert W model accurately describes attenuation of both monoenergetic radiation and (kilovoltage) polyenergetic beams (under narrow-beam geometry).

An empirical model of diagnostic x-ray attenuation under narrow-beam geometry.

Science.gov (United States)

Mathieu, Kelsey B; Kappadath, S Cheenu; White, R Allen; Atkinson, E Neely; Cody, Dianna D

2011-08-01

The purpose of this study was to develop and validate a mathematical model to describe narrow-beam attenuation of kilovoltage x-ray beams for the intended applications of half-value layer (HVL) and quarter-value layer (QVL) estimations, patient organ shielding, and computer modeling. An empirical model, which uses the Lambert W function and represents a generalized Lambert-Beer law, was developed. To validate this model, transmission of diagnostic energy x-ray beams was measured over a wide range of attenuator thicknesses [0.49-33.03 mm Al on a computed tomography (CT) scanner, 0.09-1.93 mm Al on two mammography systems, and 0.1-0.45 mm Cu and 0.49-14.87 mm Al using general radiography]. Exposure measurements were acquired under narrow-beam geometry using standard methods, including the appropriate ionization chamber, for each radiographic system. Nonlinear regression was used to find the best-fit curve of the proposed Lambert W model to each measured transmission versus attenuator thickness data set. In addition to validating the Lambert W model, we also assessed the performance of two-point Lambert W interpolation compared to traditional methods for estimating the HVL and QVL [i.e., semi-logarithmic (exponential) and linear interpolation]. The Lambert W model was validated for modeling attenuation versus attenuator thickness with respect to the data collected in this study (R2 > 0.99). Furthermore, Lambert W interpolation was more accurate and less sensitive to the choice of interpolation points used to estimate the HVL and/or QVL than the traditional methods of semilogarithmic and linear interpolation. The proposed Lambert W model accurately describes attenuation of both monoenergetic radiation and (kilovoltage) polyenergetic beams (under narrow-beam geometry).

Shielded room measurements, Final report

Energy Technology Data Exchange (ETDEWEB)

Stanton, J.S.

1949-02-22

The attenuation of electro-statically and electro-magnetically shielded rooms in the ``E,`` ``R,`` ``I,`` and ``T`` Buildings was measured so that corrective measure could be taken if the attenuation was found to be low. If remedial measures could not be taken, the shortcomings of the rooms would be known. Also, the men making the measurements should oversee construction and correct errors at the time. The work was performed by measuring the attenuation at spot frequencies over the range of from 150 kilocycles to 1280 megacycles with suitable equipment mounted in small rubber-tried trucks. The attenuation was determined by ``before and after`` shielding and/or ``door open and door closed`` measurements after installation of copper shielding. In general, attenuation in the frequency range of approximately 10 to 150 mc. was good and was of the order expected. At frequencies in the range of 150 mc. to 1280 mc., the attenuation curve was more erratic; that is, at certain frequencies a severe loss of attenuation was noted, while at others, the attenuation was very good. This was mainly due to poor or faulty seals around doors and pass windows. These poor seals existed in the ``T,`` ``E,`` and ``I`` Buildings because the doors were fitted improperly and somewhat inferior material was used. By experience from these difficulties, both causes were corrected in the ``R`` Building, which resulted in the improvement of the very high frequency (v.h.f.) range in this building. In some specific cases, however, the results were about the same. For the range of frequencies below approximately 10 mc., the attenuation, in almost all cases, gradually decreased as the frequency decreased and reached a minimum at .3 to 1.0 mc. This loss of attenuation was attributed to multiple grounding caused by moisture in the insulating timbers and will gradually decrease as the wood dries out.

Statistical Analysis of Instantaneous Frequency Scaling Factor as Derived From Optical Disdrometer Measurements At KQ Bands

Science.gov (United States)

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

2016-01-01

The rain rate data and statistics of a location are often used in conjunction with models to predict rain attenuation. However, the true attenuation is a function not only of rain rate, but also of the drop size distribution (DSD). Generally, models utilize an average drop size distribution (Laws and Parsons or Marshall and Palmer. However, individual rain events may deviate from these models significantly if their DSD is not well approximated by the average. Therefore, characterizing the relationship between the DSD and attenuation is valuable in improving modeled predictions of rain attenuation statistics. The DSD may also be used to derive the instantaneous frequency scaling factor and thus validate frequency scaling models. Since June of 2014, NASA Glenn Research Center (GRC) and the Politecnico di Milano (POLIMI) have jointly conducted a propagation study in Milan, Italy utilizing the 20 and 40 GHz beacon signals of the Alphasat TDP#5 Aldo Paraboni payload. The Ka- and Q-band beacon receivers provide a direct measurement of the signal attenuation while concurrent weather instrumentation provides measurements of the atmospheric conditions at the receiver. Among these instruments is a Thies Clima Laser Precipitation Monitor (optical disdrometer) which yields droplet size distributions (DSD); this DSD information can be used to derive a scaling factor that scales the measured 20 GHz data to expected 40 GHz attenuation. Given the capability to both predict and directly observe 40 GHz attenuation, this site is uniquely situated to assess and characterize such predictions. Previous work using this data has examined the relationship between the measured drop-size distribution and the measured attenuation of the link]. The focus of this paper now turns to a deeper analysis of the scaling factor, including the prediction error as a function of attenuation level, correlation between the scaling factor and the rain rate, and the temporal variability of the drop size

Recent Progress Validating the HADES Model of LLNL's HEAF MicroCT Measurements

Energy Technology Data Exchange (ETDEWEB)

White, W. T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Bond, K. C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Lennox, K. P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Aufderheide, M. B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Seetho, I. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Roberson, G. P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2014-07-17

This report compares recent HADES calculations of x-ray linear attenuation coefficients to previous MicroCT measurements made at Lawrence Livermore National Laboratory’s High Energy Applications Facility (HEAF). The chief objective is to investigate what impact recent changes in HADES modeling have on validation results. We find that these changes have no obvious effect on the overall accuracy of the model. Detailed comparisons between recent and previous results are presented.

Effect of sample thickness on the measured mass attenuation coefficients of some compounds and elements for 59.54, 661.6 and 1332.5 keV gamma-rays

CERN Document Server

El-Rahman, M A; Abdel-Hady, Y L; Kamel, N

2000-01-01

Measurements have been made to determine gamma-rays attenuation coefficients very accurately by using an extremely narrow-collimated-beam transmission method. The effect of the sample thickness on the measured values of the mass attenuation coefficients (mu/rho) cm sup 2 /g of perspex, bakelite, paraffin, Al, Cu, Pb and Hg have been investigated at three different gamma-ray energies (59.54, 661.6 and 1332.5 keV). It is seen that for these chosen materials (mu/rho) remains constant in good agreement with the theoretical values up to 3 mean free paths and after that (mu/rho) values for Cu, Pb and Hg decrease with further increase in the absorber thickness. This result may be attributed to the increase in the number of coherent small-angle scattering photons which reach the detector.

Attenuation maps for SPECT determined using cone beam transmission computed tomography

International Nuclear Information System (INIS)

Manglos, S.H.; Bassano, D.A.; Duxbury, C.E.; Capone, R.B.

1990-01-01

This paper presents a new method for measuring non-uniform attenuation maps, using a cone beam geometry CT scan acquired on a standard rotating gamma camera normally used for SPECT imaging. The resulting map is intended for use in non-uniform attenuation compensation of SPECT images. The method was implemented using a light-weight point source holder attached to the camera. A cone beam collimator may be used on the gamma camera, but the cone beam CT scans may also be acquired without collimator. In either implementation, the advantages include very high efficiency and resolution limited not by the collimator but by the intrinsic camera resolution (about 4 mm). Several phantoms tested the spatial uniformity, noise, linearity as a function of attenuation coefficient, and spatial resolution. Good quality attenuation maps were obtained, at least for the central slices where no truncation was present

Polymer composites with carbon nanotube for application of radiation attenuator in medical procedures

Energy Technology Data Exchange (ETDEWEB)

Fontainha, C.C.P.; Nunes, M.; Rosas, V.A., E-mail: crissia@gmail.com [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Anatomia e Imagem; Furtado, C.A.; Faria, L.O. [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

2017-07-01

Medical radiology offers great benefit to patients, however, the radiation contributes for the workers and individuals exposure, significantly increasing dose to population. New attenuators materials have been widely investigated for radiation shielding to apply in medical procedures. Polymeric composites filled with attenuating metals and functionalized with carbon nanotubes (NTC) are being largely developed. In this work, composites were produced for radiation attenuation in radiodiagnostic imaging procedures. Two types of polymer matrices, polyvinylidene fluoride, PVDF, and its copolymer, poly(vinylidene-trifluorylene fluoride), P(VDF-TrFE), were filled bismuth oxide nanoparticles. Carbon nanotubes were added with different concentrations at the solution of attenuator metal under controlled magnetic stirring. The composites were characterized by differential heat flow scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and dispersive energy X-ray spectrometry (EDS) for thermal analysis. In this setup, one reference measure is directly exposed to the x-rays being diffracted by single crystal of Si (111). Another measure the attenuated beam is performed with the composite sample under detector. The samples present a good dispersion of the attenuator metal and the nanotube carbon. On the other hand, composites with PVDF matrix lost their plasticity, stiffening their structure, becoming brittle, even using the same methodology of synthesis. The P(VDF-Trfe) matrix showed better maleability than PVDF matrix. The cheaptube dispersion in the P(VDF-Trfe) matrix presented better than the 3100 carbon nanotubes. The attenuation for 8.047 keV monoenergetic photons was about 90% to 100 μm thickness for all composites. (author)

Polymer composites with carbon nanotube for application of radiation attenuator in medical procedures

International Nuclear Information System (INIS)

Fontainha, C.C.P.; Nunes, M.; Rosas, V.A.

2017-01-01

Medical radiology offers great benefit to patients, however, the radiation contributes for the workers and individuals exposure, significantly increasing dose to population. New attenuators materials have been widely investigated for radiation shielding to apply in medical procedures. Polymeric composites filled with attenuating metals and functionalized with carbon nanotubes (NTC) are being largely developed. In this work, composites were produced for radiation attenuation in radiodiagnostic imaging procedures. Two types of polymer matrices, polyvinylidene fluoride, PVDF, and its copolymer, poly(vinylidene-trifluorylene fluoride), P(VDF-TrFE), were filled bismuth oxide nanoparticles. Carbon nanotubes were added with different concentrations at the solution of attenuator metal under controlled magnetic stirring. The composites were characterized by differential heat flow scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and dispersive energy X-ray spectrometry (EDS) for thermal analysis. In this setup, one reference measure is directly exposed to the x-rays being diffracted by single crystal of Si (111). Another measure the attenuated beam is performed with the composite sample under detector. The samples present a good dispersion of the attenuator metal and the nanotube carbon. On the other hand, composites with PVDF matrix lost their plasticity, stiffening their structure, becoming brittle, even using the same methodology of synthesis. The P(VDF-Trfe) matrix showed better maleability than PVDF matrix. The cheaptube dispersion in the P(VDF-Trfe) matrix presented better than the 3100 carbon nanotubes. The attenuation for 8.047 keV monoenergetic photons was about 90% to 100 μm thickness for all composites. (author)

Nonlinear inversion of borehole-radar tomography data to reconstruct velocity and attenuation distribution in earth materials

Science.gov (United States)

Zhou, C.; Liu, L.; Lane, J.W.

2001-01-01

A nonlinear tomographic inversion method that uses first-arrival travel-time and amplitude-spectra information from cross-hole radar measurements was developed to simultaneously reconstruct electromagnetic velocity and attenuation distribution in earth materials. Inversion methods were developed to analyze single cross-hole tomography surveys and differential tomography surveys. Assuming the earth behaves as a linear system, the inversion methods do not require estimation of source radiation pattern, receiver coupling, or geometrical spreading. The data analysis and tomographic inversion algorithm were applied to synthetic test data and to cross-hole radar field data provided by the US Geological Survey (USGS). The cross-hole radar field data were acquired at the USGS fractured-rock field research site at Mirror Lake near Thornton, New Hampshire, before and after injection of a saline tracer, to monitor the transport of electrically conductive fluids in the image plane. Results from the synthetic data test demonstrate the algorithm computational efficiency and indicate that the method robustly can reconstruct electromagnetic (EM) wave velocity and attenuation distribution in earth materials. The field test results outline zones of velocity and attenuation anomalies consistent with the finding of previous investigators; however, the tomograms appear to be quite smooth. Further work is needed to effectively find the optimal smoothness criterion in applying the Tikhonov regularization in the nonlinear inversion algorithms for cross-hole radar tomography. ?? 2001 Elsevier Science B.V. All rights reserved.

Touch Attenuates Infants' Physiological Reactivity to Stress

Science.gov (United States)

Feldman, Ruth; Singer, Magi; Zagoory, Orna

2010-01-01

Animal studies demonstrate that maternal touch and contact regulate infant stress, and handling during periods of maternal deprivation attenuates the stress response. To measure the effects of touch on infant stress reactivity during simulated maternal deprivation, 53 dyads were tested in two paradigms: still-face (SF) and still-face with maternal…

Met-myoglobin formation, accumulation, degradation, and myoglobin oxygenation monitoring based on multiwavelength attenuance measurement in porcine meat

Science.gov (United States)

Nguyen, Thien; Phan, Kien Nguyen; Lee, Jee-Bum; Kim, Jae Gwan

2016-05-01

We propose a simple, rapid, and nondestructive method to investigate formation, accumulation, and degradation of met-myoglobin (met-Mb) and myoglobin oxygenation from the interior of porcine meat. For the experiment, color photos and attenuance spectra of porcine meat (well-bled muscle, fat, and mixed) were collected daily to perform colorimetric analysis and to obtain the differences of attenuance between 578 and 567 nm (A578-A567) and between 615 and 630 nm (A630-A615), respectively. Oxy-, deoxy-, and met-myoglobin concentration changes over storage time were also calculated using Beer-Lamberts' law with reflectance intensities at 557, 582, and 630 nm. The change of A578-A567 was well matched with the change of myoglobin oxygenation, and the change of A630-A615 corresponded well with the formation and degradation of met-Mb. In addition, attenuation differences, A578-A567 and A630-A615, were able to show the formation of met-Mb earlier than colorimetric analysis. Therefore, the attenuance differences between wavelengths can be indicators for estimating myoglobin oxygenation and met-Mb formation, accumulation, and degradation, which enable us to design a simple device to monitor myoglobin activities in porcine meat.

Microdosimetric spectra measurements of JANUS neutrons

Energy Technology Data Exchange (ETDEWEB)

Marshall, I.R.; Williamson, F.S.

1985-01-01

Neutron radiation from the JANUS reactor at Argonne National Laboratory is being used with increasing frequency for major biological experiments. The fast neutron spectrum has a Kerma-weighted mean energy of 0.8 MeV and low gamma-ray contamination. In 1984 the JANUS fission converter plate of highly enriched uranium was replaced by one made of low-enriched uranium. We recorded microdosimetric spectra at several different positions in the high-flux irradiation room of JANUS before the change of the converter plate. Each set of measurements consisted of spectra taken at three different site diameters (0.5, 1.0, and 5.0 ..mu..m) and in both ''attenuator up'' and ''attenuator down'' configurations. At two conventional dosimetry reference positions, two sets of measurements were recorded. At three biological reference positions, measurements simulating several biological irradiation conditions, were taken. The dose rate at each position was estimated and compared with dose rates obtained previously by conventional dosimetry. Comparison of the different measurements showed no major change in spectra as a function of position or irradiation condition. First results from similar sets of measurements recorded after the installment of the new converter plate indicate no major change in the spectra. 11 refs., 4 figs., 5 tabs.

Microdosimetric spectra measurements of JANUS neutrons

International Nuclear Information System (INIS)

Marshall, I.R.; Williamson, F.S.

1985-01-01

Neutron radiation from the JANUS reactor at Argonne National Laboratory is being used with increasing frequency for major biological experiments. The fast neutron spectrum has a Kerma-weighted mean energy of 0.8 MeV and low gamma-ray contamination. In 1984 the JANUS fission converter plate of highly enriched uranium was replaced by one made of low-enriched uranium. We recorded microdosimetric spectra at several different positions in the high-flux irradiation room of JANUS before the change of the converter plate. Each set of measurements consisted of spectra taken at three different site diameters (0.5, 1.0, and 5.0 μm) and in both ''attenuator up'' and ''attenuator down'' configurations. At two conventional dosimetry reference positions, two sets of measurements were recorded. At three biological reference positions, measurements simulating several biological irradiation conditions, were taken. The dose rate at each position was estimated and compared with dose rates obtained previously by conventional dosimetry. Comparison of the different measurements showed no major change in spectra as a function of position or irradiation condition. First results from similar sets of measurements recorded after the installment of the new converter plate indicate no major change in the spectra. 11 refs., 4 figs., 5 tabs

Anomalous ultrasonic attenuation and velocity change in LaAl2

International Nuclear Information System (INIS)

Federle, G.; Dransfeld, K.; Boemmel, H.E.; Roedhammer, P.

1980-01-01

The attenuation and velocity of longitudinal waves has been measured in superconducting and normal LaAl 2 in the frequency range from 15 to 225 MHz. Both in the superconducting and in the normal state an unusually large damping has been found superimposed on the relatively small attenuation due to the well known electron-phonon interaction. On cooling into the superconducting state the attenuation starts to drop only at temperatures well below Tsub(c) and - as in insulating glasses - it rises again below 0.8K. It is suggested that this indicates that two-level systems similar to the ones found in amorphous superconductors may be present in the crystalline LaAl 2 sample and are responsible for the observed acoustic anomalies. (author)

Mass attenuation coefficients of X-rays in different medicinal plants

Energy Technology Data Exchange (ETDEWEB)

Morabad, R B [Department of Post-Graduate Studies and Research in Physics, Gulbarga University, Gulbarga 585106, Karnataka (India); Kerur, B.R. [Department of Post-Graduate Studies and Research in Physics, Gulbarga University, Gulbarga 585106, Karnataka (India)], E-mail: kerurbrk@yahoo.com

2010-02-15

The mass attenuation coefficients of specific parts of several plants, (fruits, leaves, stem and seeds) often used as medicines in the Indian herbal system, have been measured employing NaI (TI)) detector. The electronic setup used is a NaI (TI) detector, which is coupled to MCA for analysis of the spectrum. A source of {sup 241}Am is used to get X-rays in the energy range 8-32 keV from Cu, Rb, Mo, Ag and Ba targets. In the present study, the measured mass attenuation coefficient of Ocimum sanctum, Catharanthus roseus, Trigonella foenum-graecum, Azadirachta indica, Aegle marmelos, Zingiber officinalis, Emblica officinalis, Anacardium occidentale, Momordica charantia and Syzygium cumini show a linear relation with the energy.

Mass attenuation coefficients of X-rays in different medicinal plants

International Nuclear Information System (INIS)

Morabad, R.B.; Kerur, B.R.

2010-01-01

The mass attenuation coefficients of specific parts of several plants, (fruits, leaves, stem and seeds) often used as medicines in the Indian herbal system, have been measured employing NaI (TI)) detector. The electronic setup used is a NaI (TI) detector, which is coupled to MCA for analysis of the spectrum. A source of 241 Am is used to get X-rays in the energy range 8-32 keV from Cu, Rb, Mo, Ag and Ba targets. In the present study, the measured mass attenuation coefficient of Ocimum sanctum, Catharanthus roseus, Trigonella foenum-graecum, Azadirachta indica, Aegle marmelos, Zingiber officinalis, Emblica officinalis, Anacardium occidentale, Momordica charantia and Syzygium cumini show a linear relation with the energy.

Using X-ray transmission/attenuation to quantify fluid absorption in cracked concrete

DEFF Research Database (Denmark)

Weiss, Jason; Geiker, Mette R.; Hansen, Kurt Kielsgaard

2015-01-01

Cracks can alter the rate of fluid transport in concrete. Unfortunately, however, quantitative information is lacking to provide definitive statements regarding the extent to which cracks reduce durability or long-term performance. This paper describes a study that used X-ray transmission......-ray attenuation measurements were taken using a grid of points around the crack. By repeating this measurement and comparing the change in X-ray transmission/attenuation, the ingress of the fluid could be determined by locating the position of the moisture front. An approach is presented to determine the geometry...

Survival probability of precipitations and rain attenuation in tropical and equatorial regions

Science.gov (United States)

Mohebbi Nia, Masoud; Din, Jafri; Panagopoulos, Athanasios D.; Lam, Hong Yin

2015-08-01

This contribution presents a stochastic model useful for the generation of a long-term tropospheric rain attenuation time series for Earth space or a terrestrial radio link in tropical and equatorial heavy rain regions based on the well-known Cox-Ingersoll-Ross model previously employed in research in the fields of finance and economics. This model assumes typical gamma distribution for rain attenuation in heavy rain climatic regions and utilises the temporal dynamic of precipitation collected in equatorial Johor, Malaysia. Different formations of survival probability are also discussed. Furthermore, the correlation between these probabilities and the Markov process is determined, and information on the variance and autocorrelation function of rain events with respect to the particular characteristics of precipitation in this area is presented. The proposed technique proved to preserve the peculiarities of precipitation for an equatorial region and reproduce fairly good statistics of the rain attenuation correlation function that could help to improve the prediction of dynamic characteristics of rain fade events.

Evaluation of downwelling diffuse attenuation coefficient algorithms in the Red Sea

KAUST Repository

Tiwari, Surya Prakash

2016-05-07

Despite the importance of the optical properties such as the downwelling diffuse attenuation coefficient for characterizing the upper water column, until recently no in situ optical measurements were published for the Red Sea. Kirby et al. used observations from the Coastal Zone Color Scanner to characterize the spatial and temporal variability of the diffuse attenuation coefficient (Kd(490)) in the Red Sea. To better understand optical variability and its utility in the Red Sea, it is imperative to comprehend the diffuse attenuation coefficient and its relationship with in situ properties. Two apparent optical properties, spectral remote sensing reflectance (Rrs) and the downwelling diffuse attenuation coefficient (Kd), are calculated from vertical profile measurements of downwelling irradiance (Ed) and upwelling radiance (Lu). Kd characterizes light penetration into water column that is important for understanding both the physical and biogeochemical environment, including water quality and the health of ocean environment. Our study tests the performance of the existing Kd(490) algorithms in the Red Sea and compares them against direct in situ measurements within various subdivisions of the Red Sea. Most standard algorithms either overestimated or underestimated with the measured in situ values of Kd. Consequently, these algorithms provided poor retrieval of Kd(490) for the Red Sea. Random errors were high for all algorithms and the correlation coefficients (r2) with in situ measurements were quite low. Hence, these algorithms may not be suitable for the Red Sea. Overall, statistical analyses of the various algorithms indicated that the existing algorithms are inadequate for the Red Sea. The present study suggests that reparameterizing existing algorithms or developing new regional algorithms is required to improve retrieval of Kd(490) for the Red Sea. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is

Pentoxifylline Attenuates Cardiac Remodeling Induced by Tobacco Smoke Exposure

Energy Technology Data Exchange (ETDEWEB)

Minicucci, Marcos; Oliveira, Fernando; Santos, Priscila; Polegato, Bertha; Roscani, Meliza; Fernandes, Ana Angelica; Lustosa, Beatriz; Paiva, Sergio; Zornoff, Leonardo; Azevedo, Paula, E-mail: paulasa@fmb.unesp.br [Faculdade de Medicina de Botucatu, Universidade Estadual Paulista, São Paulo, SP (Brazil)

2016-05-15

Tobacco smoke exposure is an important risk factor for cardiac remodeling. Under this condition, inflammation, oxidative stress, energy metabolism abnormalities, apoptosis, and hypertrophy are present. Pentoxifylline has anti‑inflammatory, anti-apoptotic, anti-thrombotic and anti-proliferative properties. The present study tested the hypothesis that pentoxifylline would attenuate cardiac remodeling induced by smoking. Wistar rats were distributed in four groups: Control (C), Pentoxifylline (PX), Tobacco Smoke (TS), and PX-TS. After two months, echocardiography, invasive blood pressure measurement, biochemical, and histological studies were performed. The groups were compared by two-way ANOVA with a significance level of 5%. TS increased left atrium diameter and area, which was attenuated by PX. In the isolated heart study, TS lowered the positive derivate (+dp/dt), and this was attenuated by PX. The antioxidants enzyme superoxide dismutase and glutathione peroxidase were decreased in the TS group; PX recovered these activities. TS increased lactate dehydrogenase (LDH) and decreased 3-hydroxyacyl Coenzyme A dehydrogenases (OH-DHA) and citrate synthase (CS). PX attenuated LDH, 3-OH-DHA and CS alterations in TS-PX group. TS increased IL-10, ICAM-1, and caspase-3. PX did not influence these variables. TS induced cardiac remodeling, associated with increased inflammation, oxidative stress, apoptosis, and changed energy metabolism. PX attenuated cardiac remodeling by reducing oxidative stress and improving cardiac bioenergetics, but did not act upon cardiac cytokines and apoptosis.

Landing gear noise attenuation

Science.gov (United States)

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.

Dose attenuation by a carbon fiber linac couch and modeling with a treatment planning system

International Nuclear Information System (INIS)

Sanchez Galiano, P.; Garcia Sancho, J.M.; Crelgo, D.; Pamos, M.; Fernandez, J.; Vivanco, J.

2010-01-01

The purpose of this work is to investigate the attenuation caused by a carbon fiber linac treatment couch and the ability of a commercial radiotherapy treatment planning system to simulate it. The attenuation caused by an Exact treatment couch in a Varian Clinac 2100 C/D was characterized in detail. Both 6 MV and 18 MV photon beams were studied. The treatment couch was modeled and incorporated to Elekta XiO treatment planning system. Measured and computed attenuation values were compared. As a result we found that the attenuation caused by this complex treatment couch is strongly dependent on the incidence angle of the beam. The measured attenuation values reach 16% for 6 MV and 10% for 18 MV. The model incorporated to the treatment planning software allows reducing the differences between measured and calculated data below 2.5% and 2.0% for 6 MV and 18 MV respectively. In conclusion, it is strongly recommended accounting for the perturbation caused by this carbon fiber treatment couch when the beam intersects it. The treatment planning system studied can simulate this treatment couch accurately. Clinical implementation of the described method requires a reliable procedure to reproduce the same patient geometry in the treatment delivery and planning. (Author).

Wave attenuation across a tidal marsh in San Francisco Bay

Science.gov (United States)

Foster-Martinez, Madeline R.; Lacy, Jessica; Ferner, Matthew C.; Variano, Evan A.

2018-01-01

Wave attenuation is a central process in the mechanics of a healthy salt marsh. Understanding how wave attenuation varies with vegetation and hydrodynamic conditions informs models of other marsh processes that are a function of wave energy (e.g. sediment transport) and allows for the incorporation of marshes into coastal protection plans. Here, we examine the evolution of wave height across a tidal salt marsh in San Francisco Bay. Instruments were deployed along a cross-shore transect, starting on the mudflat and crossing through zones dominated by Spartina foliosa and Salicornia pacifica. This dataset is the first to quantify wave attenuation for these vegetation species, which are abundant in the intertidal zone of California estuaries. Measurements were collected in the summer and winter to assess seasonal variation in wave attenuation. Calculated drag coefficients of S. foliosa and S. pacifica were similar, indicating equal amounts of vegetation would lead to similar energy dissipation; however, S. pacifica has much greater biomass close to the bed (<20 cm) and retains biomass throughout the year, and therefore, it causes more total attenuation. S. foliosa dies back in the winter, and waves often grow across this section of the marsh. For both vegetation types, attenuation was greatest for low water depths, when the vegetation was emergent. For both seasons, attenuation rates across S. pacifica were the highest and were greater than published attenuation rates across similar (Spartina alterniflora) salt marshes for the comparable depths. These results can inform designs for marsh restorations and management plans in San Francisco Bay and other estuaries containing these species.

Experimental comparison of gamma attenuations by glasses, lead, iron and concretes

International Nuclear Information System (INIS)

Charamathieu, Andre; Papot, Lucien

1964-08-01

The authors report the experimental determination, for lead glasses of density 3.3, 4.2, 5.2 and 6.2, of thicknesses equivalent to thicknesses given for lead, iron, ordinary concrete and barite concrete for Cobalt 60 and Caesium 137 radiations. Results are presented under the form of curves. Attenuation measurements made on this opportunity and those made on various hot cells have been compared with theoretical attenuation curves produced in another CEA document [fr

X-ray attenuation coefficient measurements for photon energies 4.508-13.375 keV in Cu, Cr and their compounds and the validity of the mixture rule

International Nuclear Information System (INIS)

Turgut, Ue.; Simsek, Oe.; Bueyuekkasap, E.; Ertugrul, M.

2004-01-01

To investigate the validity of the mixture rule which is used to compute the mass attenuation coefficients in compounds, the total mass attenuation coefficients for Cu, Cr elements and Cu 2 O, CuC 2 O 4 , CuCl 2 ·2H 2 O, Cu(C 2 H 3 O 2 ) 2 ·H 2 O, Cr 2 O 3 , Cr(NO 3 ) 3 , Cr 2 (SO 4 ) 3 ·H 2 O, Cr 3 (CH 3 CO 7 )(OH) 2 compounds were measured at photon energies between 4.508 and 13.375 keV by using the secondary excitation method. Ti, Mn, Fe, Ni, Zn, Ge, As, Rb elements were used as secondary exciters. 59.5 keV gamma rays emitted from an 241 Am annular source were used to excite the secondary exciters and Kα (K-L 3 , L 2 ) rays emitted from the secondary exciter were counted by a Si(Li) detector with a resolution of 160 eV at 5.9 keV. Our measurements indicate that the mixture rule is not a suitable method for the computation of mass attenuation coefficients of compounds especially at an energy that is near the absorption edge. Obtained values were compared with theoretical values

Assessment of endothelial function and myocardial flow reserve using 15O-water PET without attenuation correction

International Nuclear Information System (INIS)

Tuffier, Stephane; Joubert, Michael; Bailliez, Alban; Legallois, Damien; Belin, Annette; Redonnet, Michel; Agostini, Denis; Manrique, Alain

2016-01-01

Myocardial blood flow (MBF) measurement using positron emission tomography (PET) from the washout rate of 15 O-water is theoretically independent of tissue attenuation. The aim of this study was to evaluate the impact of not using attenuation correction in the assessment of coronary endothelial function and myocardial flow reserve (MFR) using 15 O-water PET. We retrospectively processed 70 consecutive 15 O-water PET examinations obtained at rest and during cold pressor testing (CPT) in patients with dilated cardiomyopathy (n = 58), or at rest and during adenosine infusion in heart transplant recipients (n = 12). Data were reconstructed with attenuation correction (AC) and without attenuation correction (NAC) using filtered backprojection, and MBF was quantified using a single compartmental model. The agreement between AC and NAC data was assessed using Lin's concordance correlation coefficient followed by Bland-Altman plot analysis. Regarding endothelial function, NAC PET showed poor reproducibility and poor agreement with AC PET data. Conversely, NAC PET demonstrated high reproducibility and a strong agreement with AC PET for the assessment of MFR. Non-attenuation-corrected 15 O-water PET provided an accurate measurement of MFR compared to attenuation-corrected PET. However, non-attenuation-corrected PET data were less effective for the assessment of endothelial function using CPT in this population. (orig.)

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

Science.gov (United States)

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

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

Directory of Open Access Journals (Sweden)

Jian Kang

2012-10-01

Full Text Available 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.

Enhancement of the safety of live influenza vaccine by attenuating mutations from cold-adapted hemagglutinin

International Nuclear Information System (INIS)

Lee, Yoon Jae; Jang, Yo Han; Kim, Paul; Lee, Yun Ha; Lee, Young Jae; Byun, Young Ho; Lee, Kwang-Hee; Kim, Kyusik; Seong, Baik Lin

2016-01-01

In our previous study, X-31ca-based H5N1 LAIVs, in particular, became more virulent in mice than the X-31ca MDV, possibly by the introduction of the surface antigens of highly pathogenic H5N1 influenza virus, implying that additional attenuation is needed in this cases to increase the safety level of the vaccine. In this report we suggest an approach to further increase the safety of LAIV through additional cold-adapted mutations in the hemagglutinin. The cold-adaptation of X-31 virus resulted in four amino acid mutations in the HA. We generated a panel of 7:1 reassortant viruses each carrying the hemagglutinins with individual single amino acid mutations. We examined their phenotypes and found a major attenuating mutation, N81K. This attenuation marker conferred additional temperature-sensitive and attenuation phenotype to the LAIV. Our data indicate that the cold-adapted mutation in the HA confers additional attenuation to the LAIV strain, without compromising its productivity and immune response. - Highlights: • Cold-adaptation process induced four amino acid mutations in the HA of X-31 virus. • The four mutations in the HA also contributed to attenuation of the X-31ca virus • N81K mutation was the most significant marker for the attenuation of X-31ca virus. • Introduction of N81K mutation into H3N2 LAIV further attenuated the vaccine. • This approach provides a useful guideline for enhancing the safety of the LAIVs.

Enhancement of the safety of live influenza vaccine by attenuating mutations from cold-adapted hemagglutinin

Energy Technology Data Exchange (ETDEWEB)

Lee, Yoon Jae [Graduate Program in Biomaterials Science and Engineering, College of Life Science and Biotechnology, Yonsei University, Seoul (Korea, Republic of); Laboratory of Molecular Medicine, Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul (Korea, Republic of); Vaccine Translational Research Center, Yonsei University, Seoul (Korea, Republic of); Jang, Yo Han [Laboratory of Molecular Medicine, Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul (Korea, Republic of); Kim, Paul; Lee, Yun Ha; Lee, Young Jae [Laboratory of Molecular Medicine, Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul (Korea, Republic of); Vaccine Translational Research Center, Yonsei University, Seoul (Korea, Republic of); Byun, Young Ho; Lee, Kwang-Hee; Kim, Kyusik [Laboratory of Molecular Medicine, Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul (Korea, Republic of); Seong, Baik Lin, E-mail: blseong@yonsei.ac.kr [Graduate Program in Biomaterials Science and Engineering, College of Life Science and Biotechnology, Yonsei University, Seoul (Korea, Republic of); Laboratory of Molecular Medicine, Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul (Korea, Republic of); Vaccine Translational Research Center, Yonsei University, Seoul (Korea, Republic of)

2016-04-15

In our previous study, X-31ca-based H5N1 LAIVs, in particular, became more virulent in mice than the X-31ca MDV, possibly by the introduction of the surface antigens of highly pathogenic H5N1 influenza virus, implying that additional attenuation is needed in this cases to increase the safety level of the vaccine. In this report we suggest an approach to further increase the safety of LAIV through additional cold-adapted mutations in the hemagglutinin. The cold-adaptation of X-31 virus resulted in four amino acid mutations in the HA. We generated a panel of 7:1 reassortant viruses each carrying the hemagglutinins with individual single amino acid mutations. We examined their phenotypes and found a major attenuating mutation, N81K. This attenuation marker conferred additional temperature-sensitive and attenuation phenotype to the LAIV. Our data indicate that the cold-adapted mutation in the HA confers additional attenuation to the LAIV strain, without compromising its productivity and immune response. - Highlights: • Cold-adaptation process induced four amino acid mutations in the HA of X-31 virus. • The four mutations in the HA also contributed to attenuation of the X-31ca virus • N81K mutation was the most significant marker for the attenuation of X-31ca virus. • Introduction of N81K mutation into H3N2 LAIV further attenuated the vaccine. • This approach provides a useful guideline for enhancing the safety of the LAIVs.

Attenuation coefficients of soils and some building materials of Bangladesh in the energy range 276-1332 keV

International Nuclear Information System (INIS)

Alam, M.N.; Miah, M.M.H.; Chowdhury, M.I.; Kamal, M.; Ghose, S.; Rahman, Runi

2001-01-01

The linear and mass attenuation coefficients of different types of soil, sand, building materials and heavy beach mineral samples from the Chittagong and Cox's Bazar area of Bangladesh were measured using a high-resolution HPGe detector and the γ-ray energies 276.1, 302.8, 356.0, 383.8, 661.6 and 1173.2 and 1332.5 keV emitted from point sources of 133 Ba, 137 Cs and 60 Co, respectively. The linear attenuation coefficients show a linear relationship with the corresponding densities of the samples studied. The variations of the mass attenuation coefficient with γ-ray energy were exponential in nature. The measured mass attenuation coefficient values were compared with measurements made in other countries for similar kinds of materials. The values are in good agreement with each other in most cases

Boundary layer attenuation in turbulent sodium flows

International Nuclear Information System (INIS)

Tenchine, D.

1994-01-01

Temperature fluctuations are produced in the sodium coolant of Liquid Metal Reactors when flows at different temperatures are mixing. That occurs in various areas of the reactor plant, in the primary and the secondary circuits. This paper deals with secondary circuit pipings, specifically the Superphenix steam generator outlet. The possibility of thermal striping in this area is studied because of the mixing of a main 'hot' flow surrounded by a smaller 'cold' flow in the vertical pipe located below the steam generator. This work was developed in the frame of a collaboration between CEA, EDF and FRAMATOME. The purpose of our study is to measure temperature fluctuations in the fluid and on the structures, on a sodium reduced scale model of the outlet region of the steam generator. We want to evidence the boundary layer attenuation by comparing wall and fluid measurements. From these experimental data, we shall propose a methodology to predict the boundary layer attenuation and the temperature fluctuations at the surface of the structure, for pipe flow configurations

Lateral variation of seismic attenuation in Sikkim Himalaya

Science.gov (United States)

Thirunavukarasu, Ajaay; Kumar, Ajay; Mitra, Supriyo

2017-01-01

We use data from local earthquakes (mb ≥ 3.0) recorded by the Sikkim broad-band seismograph network to study the frequency-dependent attenuation of the crust and uppermost mantle. These events have been relocated using body wave phase data from local and regional seismograms. The decay of coda amplitudes at a range of central frequencies (1 to 12 Hz) has been measured for 74 earthquake-receiver pairs. These measurements are combined to estimate the frequency-dependent coda Q of the form Q( f) = Q0 f η. The estimated Q0 values range from 80 to 200, with an average of 123 ± 29; and η ranges from 0.92 to 1.04, with an average of 0.98 ± 0.04. To study the lateral variation of Q0 and η, we regionalized the measured Q values by combining all the earthquake-receiver path measurements through a back projection algorithm. We consider a single back-scatter model for the coda waves with elliptical sampling and parametrize the sampled area using 0.2° square grids. A nine-point spatial smoothening (similar to spatial Gaussian filter) is applied to stabilize the inversion. This is done at every frequency to observe the spatial variation of Q( f) and subsequently combined to obtain η variations. Results of our study reveal that the Sikkim Himalaya is characterized by low Q0 (80-100) compared to the foreland basin to its south (150-200) and the Nepal Himalaya to its west (140-160). The low Q and high η in Sikkim Himalaya is attributed to extrinsic scattering attenuation from structural heterogeneity and active faults within the crust, and intrinsic attenuation due to anelasticity in the hotter lithosphere beneath the actively deforming mountain belt. Similar low Q and high η values had also been observed in northwest and Garhwal-Kumaun Himalaya.

Attenuation and Dispersion in Earth's Materials

Science.gov (United States)

Gueguen, Y.

2012-04-01

One of the last challenges of Pr. Luigi Burlini has been to set up an experimental apparatus that would measure elastic wave attenuation under high pressure conditions. This project has since been developed by his colleagues and students at ETH. As a tribute to Luigi Burlini, this presentation aims at recalling why such measurements are important , how challenging such a project is, and what the main issues ahead are. Most of our knowledge about either crustal layers (seismic exploration) or deeper layers (seismology) results from data related to elastic wave propagation inside the Earth. The large amount of available data as well as the huge capability of computers are such that descriptions in terms of isotropic homogeneous layers appear to be very crude today. Anisotropic, heterogeneous models are reported at various scales. In addition, accounting for wave attenuation (the Q factor) is potentially of great interest. The Q factor is highly sensitive to processes that involve some departure from perfect elasticity. Its knowledge may provide information on possible fluid content, temperature, etc. This is because various processes may dissipate energy (and thus lower Q value) as a result of fluid flow, solid flow, etc., depending on the precise P-T conditions at depth. This points immediately to the theoretical challenge of Q investigations: there are many possible ways for a rock to not behave as a perfect elastic body. To model these various mechanisms and identify in which conditions they can take place is a first major challenge. The second challenge is on the experimental ground. What is looked for is to get low frequencies (f close to seismic frequencies) Q data on crustal (or mantle) rocks at high pressure P-high temperature T. Experiments in such highT-high P-low f conditions are extremely difficult to perform. Only in Canberra (I. Jackson) and now in Zurich such conditions have been achieved. Attenuation and dispersion (frequency dependence) of elastic

Bone densitometry by gamma ray attenuation measurement. Development of an apparatus for use on medullary casualties

International Nuclear Information System (INIS)

Berard, E.J.-J.

1975-01-01

We proposed to follow changes in the bone mineral content of medullary damage cases by measuring the attenuation of a monoenergetic gamma ray according to the Cameron and Sorenson technique. Apart from their high cost, existing instruments are not designed for this bedside observation of patients. Our aim was therefore to design and develop an easily portable, inexpensive apparatus. The γ radiation is supplied by a sealed 125 I source fitted with a narrow collimator. The battery-operated scintillation detector is that used to detect post-operative phlebites after injection of radio-fibrinogen. The source-detector unit can move to allow a transverse bone mineral content measurement. Data from the detector are processed electronically and the results given: - either graphically on a tracing board which gives an area proportional to the bone mineral content, - or numerically by means of an integrator computing this area and supplying the linear bone density directly. Experiments carried out in vivo showed the apparatus to be sensitive and the measurements reproducible, the results obtained being comparable with those of other authors. Using pieces of embalmed bone moreover an excellent correlation was observed between the bone mineral content obtained after incineration and the results displayed by our apparatus, which can therefore be calibrated [fr

Agmatine attenuates the discriminative stimulus and hyperthermic effects of methamphetamine in male rats.

Science.gov (United States)

Thorn, David A; Li, Jiuzhou; Qiu, Yanyan; Li, Jun-Xu

2016-09-01

Methamphetamine abuse remains an alarming public heath challenge, with no approved pharmacotherapies available. Agmatine is a naturally occurring cationic polyamine that has previously been shown to attenuate the rewarding and psychomotor-sensitizing effects of methamphetamine. This study examined the effects of agmatine on the discriminative stimulus and hyperthermic effects of methamphetamine. Adult male rats were trained to discriminate 0.32 mg/kg methamphetamine from saline. Methamphetamine dose dependently increased drug-associated lever responding. The nonselective dopamine receptor antagonist haloperidol (0.1 mg/kg) significantly attenuated the discriminative stimulus effects of methamphetamine (5.9-fold rightward shift). Agmatine (10-100 mg/kg) did not substitute for methamphetamine, but significantly attenuated the stimulus effects of methamphetamine, leading to a maximum of a 3.5-fold rightward shift. Acute 10 mg/kg methamphetamine increased the rectal temperature by a maximum of 1.96±0.17°C. Agmatine (10-32 mg/kg) pretreatment significantly attenuated the hyperthermic effect of methamphetamine. Agmatine (10 mg/kg) also significantly reversed methamphetamine-induced temperature increase. Together, these results support further exploration of the value that agmatine may have for the treatment of methamphetamine abuse and overdose.

Empirical formulae for mass attenuation and energy absorption coefficients from 1 keV to 20 MeV

International Nuclear Information System (INIS)

Manjunatha, H.C.; Sowmya, N.; Seenappa, L.; Sridhar, K.N.; Hanumantharayappa, C.

2017-01-01

Mass attenuation and energy absorption coefficients represents attenuation and absorption of X-rays and gamma rays in the material medium. A new empirical formula is proposed for mass attenuation and energy absorption coefficients in the region 1 < Z < 92 and from 1 keV to 20 MeV. The mass attenuation and energy absorption coefficients do not varies linearly with energy. We have performed the nonlinear regressions/nonlinear least square fittings and proposed the simple empirical relations between mass attenuation coefficients (μ/ρ) and mass energy absorption coefficients (μ en /ρ) and energy. We have compared the values produced by this formula with that of experiments. A good agreement of present formula with the experiments/previous models suggests that the present formulae could be used to evaluate mass attenuation and energy absorption coefficients in the region 1 < Z < 92. This formula is a model-independent formula and is the first of its kind that produces a mass attenuation and energy absorption coefficient values with the only simple input of energy for wide energy range 1 keV - 20 MeV in the atomic number region 1 < Z < 92. This formula is very much useful in the fields of radiation physics and dosimetry

Measurement of spectra for intra-oral X-ray beams using biological materials as attenuator

International Nuclear Information System (INIS)

Zenóbio, Madelon A.F.; Nogueira-Tavares, Maria S.; Zenóbio, Elton G.; Squair, Peterson Lima; Santos, Marcus A.P.; Silva, Teógenes A. da

2011-01-01

In diagnostic radiology, the radiation interaction probability in matter is a strong function of the X-ray energy. The knowledge of the X-ray energy spectral distribution allows optimizing the radiographic imaging system in order to obtain high quality images with as low as reasonably achievable patient doses. In this study, transmitted X-ray spectra through dentin and enamel that are existing materials in intra-oral radiology were experimentally determined in an X-ray equipment with 40–70 kV variable range. Dentin and enamel samples with 0.4–3.8 and 0.6–2.6 mm thick were used as attenuators. X-ray transmitted spectra were measured with XR-100T model CdTe detector and half-value layers (HVL) were determined. Characteristics of both dentin and enamel transmitted spectra showed that they have differences in the penetration power in matter and in the spectrum distribution. The results will be useful for phantom developments based on dentin and enamel for image quality control in dental radiology. - Highlights: ► The X-ray energy spectral distribution, optimize the radiographic imaging system. Transmitted X-ray spectra through dentin and enamel were experimentally determined. X-ray transmitted spectra were measured (XR-100T model CdTe detector). The transmitted spectra showed differences in the penetration power and spectrum distribution. Dentin and enamel transmitted spectra will be useful for phantom developments.

Coherent normalization of finger strontium XRF measurements: feasibility and limitations

Energy Technology Data Exchange (ETDEWEB)

Zamburlini, M; Pejovic-Milic, A; Chettle, D R [Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, L8S 4K1 (Canada)

2008-08-07

A non-invasive in vivo x-ray fluorescence (XRF) method of measuring bone strontium concentrations has previously been reported as a potential diagnostic tool able to detect strontium concentration in the finger and ankle bones. The feasibility of coherent normalization for {sup 125}I-source-based finger bone strontium x-ray fluorescence (XRF) measurements is assessed here by theoretical considerations and Monte Carlo simulations. Normalization would have several advantages, among which are the correction for the signal attenuation by the overlying soft tissue, and intersubject variability in the bone size and shape. The coherent normalization of bone strontium XRF measurements presents several challenges dictated by the behaviour of the coherent cross section and mass attenuation coefficient at the energies involved. It was found that the coherent normalization alone with either 22.1 keV or 35.5 keV photons was not successful in correcting for the overlying soft tissue attenuation. However, it was found that the coherent peak at 35.5 keV was able to correct effectively for variability in the finger bone size between people. Thus, it is suggested that, if the overlying soft tissue thickness can be obtained by means of an independent measurement, the 35.5 keV peak can be used to correct for the bone size, with an overall accuracy of the normalization process of better than 10%. (note)

Mass attenuation coefficient (μ/ρ), effective atomic number (Z{sub eff}) and measurement of x-ray energy spectra using based calcium phosphate biomaterials: a comparative study

Energy Technology Data Exchange (ETDEWEB)

Fernandes Z, M. A.; Da Silva, T. A.; Nogueira, M. S. [Centro de Desenvolvimento da Tecnologia Nuclear / CNEN, Pte. Antonio Carlos 6627, Belo Horizonte 31270-901, Minas Gerais (Brazil); Goncalves Z, E., E-mail: madelon@cdtn.br [Pontifice Catholic University of Minas Gerais, Av. Dom Jose Gaspar 500, Belo Horizonte 30535-901, Minas Gerais (Brazil)

2015-10-15

In dentistry, alveolar bone regeneration procedures using based calcium phosphate biomaterials have been shown effective. However,there are not reports in the literature of studies the interaction of low energy radiation in these biomaterials used as attenuator and not being then allowed a comparison between the theoretical values and experimental.The objective of this study was to determine the interaction of radiation parameters of four dental biomaterials - BioOss, Cerasorb M Dental, Straumann Boneceramic and Osteogen for diagnostic radiology qualities. As a material and methods, the composition of the biomaterials was determined by the analytical techniques. The samples with 0.181 cm to 0,297 cm thickness were experimentally used as attenuators for the measurement of the transmitted X-rays spectra in X-ray equipment with 50 to 90 kV range by spectrometric system comprising the Cd Te detector. After this procedure, the mass attenuation coefficient, the effective atomic number were determined and compared between all the specimens analyzed, using the program WinXCOM in the range of 10 to 200 keV. In all strains examined observed that the energy spectrum of x-rays transmitted through the BioOss has the mean energy slightly smaller than the others biomaterials for close thickness. The μ/ρ and Z{sub eff} of the biomaterials showed its dependence on photon energy and atomic number of the elements of the material analyzed. It is concluded according to the methodology employed in this study that the measurements of x-ray spectrum, μ/ρ and Z{sub eff} using biomaterials as attenuators confirmed that the thickness, density, composition of the samples, the incident photon energy are factors that determine the characteristics of radiation in a tissue or equivalent material. (Author)

Evaluation of frequency-dependent ultrasound attenuation in transparent medium using focused shadowgraph technique

Science.gov (United States)

Iijima, Yukina; Kudo, Nobuki

2017-07-01

Acoustic fields of a short-pulsed ultrasound propagating through a transparent medium with ultrasound attenuation were visualized by the focused shadowgraph technique. A brightness waveform and its spatial integrations were derived from a visualized field image and compared with a pressure waveform measured by a membrane hydrophone. The experimental results showed that first-order integration of the brightness wave has good agreement with the pressure waveforms. Frequency-dependent attenuation of the pulse propagating through castor oil was derived from brightness and pressure waveforms, and attenuation coefficients determined from focused shadowgraphy and hydrophone techniques showed good agreement. The results suggest the usefulness of the shadowgraph technique not only for the visualization of ultrasound fields but also for noncontact estimation of rough pressure waveforms and correct ultrasound attenuation.

PET attenuation correction for rigid MR Tx/Rx coils from 176Lu background activity

Science.gov (United States)

Lerche, Christoph W.; Kaltsas, Theodoris; Caldeira, Liliana; Scheins, Jürgen; Rota Kops, Elena; Tellmann, Lutz; Pietrzyk, Uwe; Herzog, Hans; Shah, N. Jon

2018-02-01

One challenge for PET-MR hybrid imaging is the correction for attenuation of the 511 keV annihilation radiation by the required RF transmit and/or RF receive coils. Although there are strategies for building PET transparent Tx/Rx coils, such optimised coils still cause significant attenuation of the annihilation radiation leading to artefacts and biases in the reconstructed activity concentrations. We present a straightforward method to measure the attenuation of Tx/Rx coils in simultaneous MR-PET imaging based on the natural 176Lu background contained in the scintillator of the PET detector without the requirement of an external CT scanner or PET scanner with transmission source. The method was evaluated on a prototype 3T MR-BrainPET produced by Siemens Healthcare GmbH, both with phantom studies and with true emission images from patient/volunteer examinations. Furthermore, the count rate stability of the PET scanner and the x-ray properties of the Tx/Rx head coil were investigated. Even without energy extrapolation from the two dominant γ energies of 176Lu to 511 keV, the presented method for attenuation correction, based on the measurement of 176Lu background attenuation, shows slightly better performance than the coil attenuation correction currently used. The coil attenuation correction currently used is based on an external transmission scan with rotating 68Ge sources acquired on a Siemens ECAT HR  +  PET scanner. However, the main advantage of the presented approach is its straightforwardness and ready availability without the need for additional accessories.

Gamma-ray self-attenuation corrections in environmental samples

International Nuclear Information System (INIS)

Robu, E.; Giovani, C.

2009-01-01

Gamma-spectrometry is a commonly used technique in environmental radioactivity monitoring. Frequently the bulk samples that should be measured differ with respect to composition and density from the reference sample used for efficiency calibration. Correction factors should be applied in these cases for activity measurement. Linear attenuation coefficients and self-absorption correction factors have been evaluated for soil, grass and liquid sources with different densities and geometries.(authors)

In-stream attenuation of neuro-active pharmaceuticals and their metabolites

Science.gov (United States)

Writer, Jeffrey; Antweiler, Ronald C.; Ferrar, Imma; Ryan, Joseph N.; Thurman, Michael

2013-01-01

In-stream attenuation was determined for 14 neuro-active pharmaceuticals and associated metabolites. Lagrangian sampling, which follows a parcel of water as it moves downstream, was used to link hydrological and chemical transformation processes. Wastewater loading of neuro-active compounds varied considerably over a span of several hours, and thus a sampling regime was used to verify that the Lagrangian parcel was being sampled and a mechanism was developed to correct measured concentrations if it was not. In-stream attenuation over the 5.4-km evaluated reach could be modeled as pseudo-first-order decay for 11 of the 14 evaluated neuro-active pharmaceutical compounds, illustrating the capacity of streams to reduce conveyance of neuro-active compounds downstream. Fluoxetine and N-desmethyl citalopram were the most rapidly attenuated compounds (t1/2 = 3.6 ± 0.3 h, 4.0 ± 0.2 h, respectively). Lamotrigine, 10,11,-dihydro-10,11,-dihydroxy-carbamazepine, and carbamazepine were the most persistent (t1/2 = 12 ± 2.0 h, 12 ± 2.6 h, 21 ± 4.5 h, respectively). Parent compounds (e.g., buproprion, carbamazepine, lamotrigine) generally were more persistent relative to their metabolites. Several compounds (citalopram, venlafaxine, O-desmethyl-venlafaxine) were not attenuated. It was postulated that the primary mechanism of removal for these compounds was interaction with bed sediments and stream biofilms, based on measured concentrations in stream biofilms and a column experiment using stream sediments.

Experimental determination of the thickness of aluminum cascade pipes in the presence of UF{sub 6} gas during enrichment measurements

Energy Technology Data Exchange (ETDEWEB)

Lombardi, M.L., E-mail: lombardi@lanl.gov [Los Alamos National Laboratory, P.O. Box 1663, Los Alamos NM 87545 (United States); Favalli, A.; Goda, J.M.; Ianakiev, K.D.; MacArthur, D.W.; Moss, C.E. [Los Alamos National Laboratory, P.O. Box 1663, Los Alamos NM 87545 (United States)

2012-04-21

We present a method of determining the wall thickness of a pipe in a Gas Centrifuge Enrichment Plant (GCEP) when an empty pipe measurement is not feasible. Our method uses an X-ray tube for transmission measurements and a lanthanum bromide (LaBr{sub 3}) scintillation detector on the opposite side of the pipe. Two filters, molybdenum (K-edge 20.0 keV) and palladium (K-edge 24.35 keV) are used to transform the bremsstrahlung spectra produced by the X-ray tube into more useful, sharply peaked, spectra. The maximum energies of the peaks are determined by the K-edges of the filters. The attenuation properties of the uranium hexafluoride (UF{sub 6}) gas allow us to determine wall thickness by looking at the ratio of selected regions of interest (ROIs) of the Mo and Pd transmitted spectra. While the attenuation factor at these two transmission energies in the UF{sub 6} gas is nearly equal, attenuation in the aluminum pipe wall at these two energies differs by a factor of about 60. This difference allows measurement of attenuation in the pipe independent of attenuation in the UF{sub 6} gas. Feasibility studies were performed using analytical calculations, and filter thicknesses were optimized. In order to experimentally validate our attenuation measurement method, a UF{sub 6} source with variable enrichment and pipe thickness was built. We describe the experimental procedure used to verify our previous calculations and present recent results.

A game theoretic approach to a finite-time disturbance attenuation problem

Science.gov (United States)

Rhee, Ihnseok; Speyer, Jason L.

1991-01-01

A disturbance attenuation problem over a finite-time interval is considered by a game theoretic approach where the control, restricted to a function of the measurement history, plays against adversaries composed of the process and measurement disturbances, and the initial state. A zero-sum game, formulated as a quadratic cost criterion subject to linear time-varying dynamics and measurements, is solved by a calculus of variation technique. By first maximizing the quadratic cost criterion with respect to the process disturbance and initial state, a full information game between the control and the measurement residual subject to the estimator dynamics results. The resulting solution produces an n-dimensional compensator which expresses the controller as a linear combination of the measurement history. A disturbance attenuation problem is solved based on the results of the game problem. For time-invariant systems it is shown that under certain conditions the time-varying controller becomes time-invariant on the infinite-time interval. The resulting controller satisfies an H(infinity) norm bound.

Understanding the amplitudes of noise correlation measurements

Science.gov (United States)

Tsai, Victor C.

2011-01-01

Cross correlation of ambient seismic noise is known to result in time series from which station-station travel-time measurements can be made. Part of the reason that these cross-correlation travel-time measurements are reliable is that there exists a theoretical framework that quantifies how these travel times depend on the features of the ambient noise. However, corresponding theoretical results do not currently exist to describe how the amplitudes of the cross correlation depend on such features. For example, currently it is not possible to take a given distribution of noise sources and calculate the cross correlation amplitudes one would expect from such a distribution. Here, we provide a ray-theoretical framework for calculating cross correlations. This framework differs from previous work in that it explicitly accounts for attenuation as well as the spatial distribution of sources and therefore can address the issue of quantifying amplitudes in noise correlation measurements. After introducing the general framework, we apply it to two specific problems. First, we show that we can quantify the amplitudes of coherency measurements, and find that the decay of coherency with station-station spacing depends crucially on the distribution of noise sources. We suggest that researchers interested in performing attenuation measurements from noise coherency should first determine how the dominant sources of noise are distributed. Second, we show that we can quantify the signal-to-noise ratio of noise correlations more precisely than previous work, and that these signal-to-noise ratios can be estimated for given situations prior to the deployment of seismometers. It is expected that there are applications of the theoretical framework beyond the two specific cases considered, but these applications await future work.

Muscle Attenuation Is Associated With Newly Developed Hypertension in Men of African Ancestry.

Science.gov (United States)

Zhao, Qian; Zmuda, Joseph M; Kuipers, Allison L; Bunker, Clareann H; Patrick, Alan L; Youk, Ada O; Miljkovic, Iva

2017-05-01

Increased ectopic adipose tissue infiltration in skeletal muscle is associated with insulin resistance and diabetes mellitus. We evaluated whether change in skeletal muscle adiposity predicts subsequent development of hypertension in men of African ancestry, a population sample understudied in previous studies. In the Tobago Health Study, a prospective longitudinal study among men of African ancestry (age range 40-91 years), calf intermuscular adipose tissue, and skeletal muscle attenuation were measured with computed tomography. Hypertension was defined as a systolic blood pressure ≥140 mm Hg, or a diastolic blood pressure ≥90 mm Hg, or receiving antihypertensive medications. Logistic regression was performed with adjustment for age, insulin resistance, baseline and 6-year change in body mass index, baseline and 6-year change in waist circumference, and other potential confounding factors. Among 746 normotensive men at baseline, 321 (43%) developed hypertension during the mean 6.2 years of follow-up. Decreased skeletal muscle attenuation was associated with newly developed hypertension after adjustment for baseline and 6-year change of body mass index (odds ratio [95% confidence interval] per SD, 1.3 [1.0-1.6]) or baseline and 6-year change of waist circumference (odds ratio [95% confidence interval] per SD, 1.3 [1.0-1.6]). No association was observed between increased intermuscular adipose tissue and hypertension. Our novel findings show that decreased muscle attenuation is associated with newly developed hypertension among men of African ancestry, independent of general and central adiposity and insulin resistance. Further studies are needed to adjust for inflammation, visceral and other ectopic adipose tissue depots, and to confirm our findings in other population samples. © 2017 American Heart Association, Inc.

Evaluation of X ray attenuation by means of radiographic images

International Nuclear Information System (INIS)

Barros, Frieda Saicla; Paredes, Ramon S.C.; Godoi, Walmor C.; Souza, Gabriel Pinto de

2011-01-01

This paper's main goal is to adopt a qualitative methodology to evaluate the attenuation of x-radiation through X-ray images in polymeric materials plus residual lead. To determinate the images it was initially used an experimental setup at the Laboratory for Materials Diagnostics LACTEC. These results correspond to a more qualitative analysis, even with quantitative answers. Through analysis of radiographic images we can measure the intensity of radiation that goes through the plate, making possible to establish a relationship between the attenuation coefficient and the thickness of the material. (author)

MRI-guided attenuation correction in whole-body PET/MR. Assessment of the effect of bone attenuation

International Nuclear Information System (INIS)

Akbarzadeh, A.; Ay, M.R.; Ahmadian, A.; Riahi Alam, N.; Zaidi, H.

2013-01-01

Hybrid positron emission tomography (PET)/MRI presents many advantages in comparison with its counterpart PET/CT in terms of improved soft-tissue contrast, decrease in radiation exposure, and truly simultaneous and multi-parametric imaging capabilities. However, the lack of well-established methodology for MR-based attenuation correction is hampering further development and wider acceptance of this technology. We assess the impact of ignoring bone attenuation and using different tissue classes for generation of the attenuation map on the accuracy of attenuation correction of PET data. This work was performed using simulation studies based on the XCAT phantom and clinical input data. For the latter, PET and CT images of patients were used as input for the analytic simulation model using realistic activity distributions where CT-based attenuation correction was utilized as reference for comparison. For both phantom and clinical studies, the reference attenuation map was classified into various numbers of tissue classes to produce three (air, soft tissue and lung), four (air, lungs, soft tissue and cortical bones) and five (air, lungs, soft tissue, cortical bones and spongeous bones) class attenuation maps. The phantom studies demonstrated that ignoring bone increases the relative error by up to 6.8% in the body and up to 31.0% for bony regions. Likewise, the simulated clinical studies showed that the mean relative error reached 15% for lesions located in the body and 30.7% for lesions located in bones, when neglecting bones. These results demonstrate an underestimation of about 30% of tracer uptake when neglecting bone, which in turn imposes substantial loss of quantitative accuracy for PET images produced by hybrid PET/MRI systems. Considering bones in the attenuation map will considerably improve the accuracy of MR-guided attenuation correction in hybrid PET/MR to enable quantitative PET imaging on hybrid PET/MR technologies. (author)

Quantification of numerical aperture-dependence of the OCT attenuation coefficient (Conference Presentation)

Science.gov (United States)

Peinado, Liliana M.; Bloemen, Paul R.; Almasian, Mitra; van Leeuwen, Ton G.; Faber, Dirk J.

2016-03-01

Despite the improvements in early cancer diagnosis, adequate diagnostic tools for early staging of bladder cancer tumors are lacking [1]. MEMS-probes based on optical coherence tomography (OCT) provide cross-sectional imaging with a high-spatial resolution at a high-imaging speed, improving visualization of cancerous tissue [2-3]. Additionally, studies show that the measurement of localized attenuation coefficient allows discrimination between healthy and cancerous tissue [4]. We have designed a new miniaturized MEMS-probe based on OCT that will optimize early diagnosis by improving functional visualization of suspicious lesions in bladder. During the optical design phase of the probe, we have studied the effect of the numerical aperture (NA) on the OCT signal attenuation. For this study, we have employed an InnerVision Santec OCT system with several numerical apertures (25mm, 40mm, 60mm, 100mm, 150mm and 200mm using achromatic lenses). The change in attenuation coefficient was studied using 15 dilutions of intralipid ranging between 6*10-5 volume% and 20 volume%. We obtained the attenuation coefficient from the OCT images at several fixed positions of the focuses using established OCT models (e.g. single scattering with known confocal point spread function (PSF) [5] and multiple scattering using the Extended Huygens Fresnel model [6]). As a result, a non-linear increase of the scattering coefficient as a function of intralipid concentration (due to dependent scattering) was obtained for all numerical apertures. For all intralipid samples, the measured attenuation coefficient decreased with a decrease in NA. Our results suggest a non-negligible influence of the NA on the measured attenuation coefficient. [1] Khochikar MV. Rationale for an early detection program for bladder cancer. Indian J Urol 2011 Apr-Jun; 27(2): 218-225. [2] Sun J and Xie H. Review Article MEMS-Based Endoscopic Optical Coherence Tomography. IJO 2011, Article ID 825629, 12 pages. doi:10

Evaluation of transmission methodology and attenuation correction for the microPET Focus 220 animal scanner

International Nuclear Information System (INIS)

Lehnert, Wencke; Meikle, Steven R; Siegel, Stefan; Newport, Danny; Banati, Richard B; Rosenfeld, Anatoly B

2006-01-01

An accurate, low noise estimate of photon attenuation in the subject is required for quantitative microPET studies of molecular tracer distributions in vivo. In this work, several transmission-based measurement techniques were compared, including coincidence mode with and without rod windowing, singles mode with two different energy sources ( 68 Ge and 57 Co), and postinjection transmission scanning. In addition, the effectiveness of transmission segmentation and the propagation of transmission bias and noise into the emission images were examined. The 57 Co singles measurements provided the most accurate attenuation coefficients and superior signal-to-noise ratio, while 68 Ge singles measurements were degraded due to scattering from the object. Scatter correction of 68 Ge transmission data improved the accuracy for a 10 cm phantom but over-corrected for a mouse phantom. 57 Co scanning also resulted in low bias and noise in postinjection transmission scans for emission activities up to 20 MBq. Segmentation worked most reliably for transmission data acquired with 57 Co but the minor improvement in accuracy of attenuation coefficients and signal-to-noise may not justify its use, particularly for small subjects. We conclude that 57 Co singles transmission scanning is the most suitable method for measured attenuation correction on the microPET Focus 220 animal scanner

Prediction of Near-Field Wave Attenuation Due to a Spherical Blast Source

Science.gov (United States)

Ahn, Jae-Kwang; Park, Duhee

2017-11-01

Empirical and theoretical far-field attenuation relationships, which do not capture the near-field response, are most often used to predict the peak amplitude of blast wave. Jiang et al. (Vibration due to a buried explosive source. PhD Thesis, Curtin University, Western Australian School of Mines, 1993) present rigorous wave equations that simulates the near-field attenuation to a spherical blast source in damped and undamped media. However, the effect of loading frequency and velocity of the media have not yet been investigated. We perform a suite of axisymmetric, dynamic finite difference analyses to simulate the propagation of stress waves induced by spherical blast source and to quantify the near-field attenuation. A broad range of loading frequencies, wave velocities, and damping ratios are used in the simulations. The near-field effect is revealed to be proportional to the rise time of the impulse load and wave velocity. We propose an empirical additive function to the theoretical far-field attenuation curve to predict the near-field range and attenuation. The proposed curve is validated against measurements recorded in a test blast.

Measurement of acoustic attenuation in workrooms

DEFF Research Database (Denmark)

Rindel, Jens Holger

1997-01-01

Experimental work has been done in nine halls with volumes ranging from 693 to 123.978 cubic metres. The equivalent absorption area has been determined from absorption coefficients of the surfaces, calculated from reverberation time measurements and estimated from sound pressure level measurements...... in the stationary sound field produced by an omnidirectional sound source in the room. The project has shown that there is a need for a new alternative measuring method - the results based on the classical reverberation time measurements do not agree sufficiently well with the actual equivalent absorption areas...... in the rooms. But it has not been possible within the project to establish and verify an alternative method based on a simple measurement in the stationary sound field....

In vivo evidence of methamphetamine induced attenuation of brain tissue oxygenation as measured by EPR oximetry

Science.gov (United States)

Weaver, John; Yang, Yirong; Purvis, Rebecca; Weatherwax, Theodore; Rosen, Gerald M.; Liu, Ke Jian

2014-01-01

Abuse of methamphetamine (METH) is a major and significant societal problem in the US, as a number of studies have suggested that METH is associated with increased cerebrovascular events, hemorrhage or vasospasm. Although cellular and molecular mechanisms involved in METH-induced toxicity are not completely understood, changes in brain O2 may play an important role and contribute to METH-induced neurotoxicity including dopaminergic receptor degradation. Given that O2 is the terminal electron acceptor for many enzymes that are important in brain function, the impact of METH on brain tissue pO2 in vivo remains largely uncharacterized. This study investigated striatal tissue pO2 changes in male C57BL/6 mice (16–20g) following METH administration using EPR oximetry, a highly sensitive modality to measure pO2 in vivo, in situ and in real time. We demonstrate that 20 min after a single injection of METH (8 mg/kg i.v.), the striatal pO2 was reduced to 81% of the pretreatment level and exposure to METH for 3 consecutive days further attenuated striatal pO2 to 64%. More importantly, pO2 did not recover fully to control levels even 24 hrs after administration of a single dose of METH. and continual exposure to METH exacerbates the condition. We also show a reduction in cerebral blood flow associated with a decreased brain pO2 indicating an ischemic condition. Our findings suggests that administration of METH can attenuate brain tissue pO2, which may lead to hypoxic insult, thus a risk factor for METH-induced brain injury and the development of stroke in young adults. PMID:24412707

On the Attenuation of Neutrons and Photons in a Duct Filled with a Helical Plug

Energy Technology Data Exchange (ETDEWEB)

Aalto, E; Krell, Aa

1966-12-15

Neutron and gamma ray attenuation has been studied in a cylindrical duct, length/diam. ratio 7, partly (36 vol.%) filled by a helical (screw-like) plug with adjustable number of turns. The total neutron leakage through the duct decreased by a factor of six from zero to 0.5 turn, and by an additional factor of three from 0.5 to 2 turns (saturation value). The leakage with less than 0.5 turn is governed by fast flux and above 0.5 turn by epithermal flux. It is observed that the attenuation calculation in a homogenized, infinite material combined with the predicted attenuation in a duct give the measured saturation attenuation. The length coordinates used must be slightly modified in this case. The attenuation of gamma in the saturation case (3 turns) equals that predicted without the duct attenuation in a homogenized infinite material.

Transmission-less attenuation estimation from time-of-flight PET histo-images using consistency equations

Science.gov (United States)

Li, Yusheng; Defrise, Michel; Metzler, Scott D.; Matej, Samuel

2015-08-01

In positron emission tomography (PET) imaging, attenuation correction with accurate attenuation estimation is crucial for quantitative patient studies. Recent research showed that the attenuation sinogram can be determined up to a scaling constant utilizing the time-of-flight information. The TOF-PET data can be naturally and efficiently stored in a histo-image without information loss, and the radioactive tracer distribution can be efficiently reconstructed using the DIRECT approaches. In this paper, we explore transmission-less attenuation estimation from TOF-PET histo-images. We first present the TOF-PET histo-image formation and the consistency equations in the histo-image parameterization, then we derive a least-squares solution for estimating the directional derivatives of the attenuation factors from the measured emission histo-images. Finally, we present a fast solver to estimate the attenuation factors from their directional derivatives using the discrete sine transform and fast Fourier transform while considering the boundary conditions. We find that the attenuation histo-images can be uniquely determined from the TOF-PET histo-images by considering boundary conditions. Since the estimate of the attenuation directional derivatives can be inaccurate for LORs tangent to the patient boundary, external sources, e.g. a ring or annulus source, might be needed to give an accurate estimate of the attenuation gradient for such LORs. The attenuation estimation from TOF-PET emission histo-images is demonstrated using simulated 2D TOF-PET data.

Radiation attenuation by lead and nonlead materials used in radiation shielding garments

International Nuclear Information System (INIS)

McCaffrey, J. P.; Shen, H.; Downton, B.; Mainegra-Hing, E.

2007-01-01

The attenuating properties of several types of lead (Pb)-based and non-Pb radiation shielding materials were studied and a correlation was made of radiation attenuation, materials properties, calculated spectra and ambient dose equivalent. Utilizing the well-characterized x-ray and gamma ray beams at the National Research Council of Canada, air kerma measurements were used to compare a variety of commercial and pre-commercial radiation shielding materials over mean energy ranges from 39 to 205 keV. The EGSnrc Monte Carlo user code cavity.cpp was extended to provide computed spectra for a variety of elements that have been used as a replacement for Pb in radiation shielding garments. Computed air kerma values were compared with experimental values and with the SRS-30 catalogue of diagnostic spectra available through the Institute of Physics and Engineering in Medicine Report 78. In addition to garment materials, measurements also included pure Pb sheets, allowing direct comparisons to the common industry standards of 0.25 and 0.5 mm 'lead equivalent'. The parameter 'lead equivalent' is misleading, since photon attenuation properties for all materials (including Pb) vary significantly over the energy spectrum, with the largest variations occurring in the diagnostic imaging range. Furthermore, air kerma measurements are typically made to determine attenuation properties without reference to the measures of biological damage such as ambient dose equivalent, which also vary significantly with air kerma over the diagnostic imaging energy range. A single material or combination cannot provide optimum shielding for all energy ranges. However, appropriate choice of materials for a particular energy range can offer significantly improved shielding per unit mass over traditional Pb-based materials

An examination on the correction of attenuation for calculating the renal RI accumulation

International Nuclear Information System (INIS)

Onoue, Koichi; Tachibana, Keizo; Maeda, Yoshihiro; Yanoo, Sanae; Morishita, Etsuko; Kawanaka, Masahiro; Kashiwagi, Toru; Fukuchi, Minoru

1999-01-01

An examination was made on the attenuation coefficients for calculation of true renal accumulation rate together with the precision of measurement of depth in the kidney. Kidney phantom for attenuation coefficients was a 20 x 20 cm cube where water was filled and radioactivity source of 99m Tc was placed at various depths. Radioactivity was measured by four kinds of scinti-camera with the collimator LEGP and LEHR. The phantom for radioactivity accumulation in the kidney was a 10 x 5 x 1, 3 or 5 cm box where 99m Tc solution of the standard 30 MBq was filled, and subjected to radioactivity measurement from various angles. Phantom radioactivity was found corrected by the effective attenuation coefficient, 0.131 cm, within the range of 98-114% of the standard counts. The precision of measurement of the depth was examined in sideways scintigrams obtained in clinical practice and was found to have the deviation of 1.1 cm as the mean of maximum ones and the variation coefficient of 7.1%. Measured depth was found to be well correlated with estimated ones by the method of Tonnesen or Ito which had the maximum deviation of 5.4 or 3.5 cm, respectively. (K.H.)

A COMPARISON OF MEASURED AND CALCULATED GAMMA RAY ATTENUATION FOR A COMMON COUNTING GEOMETRY

International Nuclear Information System (INIS)

Gaylord, R F

2004-01-01

In order to perform quantitative gamma spectroscopy, it is necessary to know the sample-specific detection efficiency for photons as a function of energy. The detection efficiency, along with the branching ratio for the isotope and gamma ray of interest, is used to convert observed counts/second to actual disintegrations/second, and, hence, has a large effect on the accuracy of the measurement. In cases where the geometry of the source is simple and reproducible, such as a point source, small vial of solid, or jar of liquid, geometry-specific standards may be counted to determine the detection efficiency. In cases where the samples are large, irregular, or unique, this method generally cannot be used. For example, it is impossible to obtain a NIST-traceable standard glovebox or 55-gallon drum. In these cases, a combination of measured absolute detector efficiency and calculated sample-specific correction factors is commonly used. The correction factors may be calculated via Monte Carlo simulation of the item (the method used by Canberra's ISOCS system), or via semi-empirical calculation of matrix and container attenuations based on the thickness and composition of the container and radioactive matrix (ISOTOPIC by EG and G Ortec uses this method). The accuracy of these correction factors for specific geometries is often of vital interest when assessing the quality of gamma spectroscopy data. During the Building 251 Risk-Reduction Project, over 100 samples of high activity actinides will be characterized via gamma spectroscopy, typically without removing the material from the current storage containers. Most of the radioactive materials in B-251 are stored in cylindrical stainless steel canisters (called USV containers, after the Underground Storage Vaults they are commonly stored in), 13 cm in diameter, by 28 cm high, with walls that are 1.8 mm thick. While the actual samples have a variety of configurations inside the USV container, a very common configuration is

Phages can constrain protist predation-driven attenuation of Pseudomonas aeruginosa virulence in multienemy communities

Science.gov (United States)

Friman, Ville-Petri; Buckling, Angus

2014-01-01

The coincidental theory of virulence predicts that bacterial pathogenicity could be a by-product of selection by natural enemies in environmental reservoirs. However, current results are ambiguous and the simultaneous impact of multiple ubiquitous enemies, protists and phages on virulence evolution has not been investigated previously. Here we tested experimentally how Tetrahymena thermophila protist predation and PNM phage parasitism (bacteria-specific virus) alone and together affect the evolution of Pseudomonas aeruginosa PAO1 virulence, measured in wax moth larvae. Protist predation selected for small colony types, both in the absence and presence of phage, which showed decreased edibility to protists, reduced growth in the absence of enemies and attenuated virulence. Although phage selection alone did not affect the bacterial phenotype, it weakened protist-driven antipredatory defence (biofilm formation), its associated pleiotropic growth cost and the correlated reduction in virulence. These results suggest that protist selection can be a strong coincidental driver of attenuated bacterial virulence, and that phages can constrain this effect owing to effects on population dynamics and conflicting selection pressures. Attempting to define causal links such as these might help us to predict the cold and hot spots of coincidental virulence evolution on the basis of microbial community composition of environmental reservoirs. PMID:24671085

Intracoronary imaging using attenuation-compensated optical coherence tomography allows better visualisation of coronary artery diseases

Energy Technology Data Exchange (ETDEWEB)

Foin, Nicolas, E-mail: nicolas.foin@gmail.com [International Centre for Circulatory Health, Imperial College London, W2 1LA London (United Kingdom); Mari, Jean Martial [University College London, London (United Kingdom); Nijjer, Sukhjinder; Sen, Sayan; Petraco, Ricardo [International Centre for Circulatory Health, Imperial College London, W2 1LA London (United Kingdom); Ghione, Matteo; Di Mario, Carlo [Biomedical Research Unit, Royal Brompton Hospital, London (United Kingdom); Davies, Justin E. [International Centre for Circulatory Health, Imperial College London, W2 1LA London (United Kingdom); Girard, Michaël J.A. [Department of Bioengineering, National University of Singapore (Singapore); Singapore Eye Research Institute (Singapore)

2013-05-15

Purpose: To allow an accurate diagnosis of coronary artery diseases by enhancing optical coherence tomography (OCT) images of atheromatous plaques using a novel automated attenuation compensation technique. Background: One of the major drawbacks of coronary OCT imaging is the rapid attenuation of the OCT signal, limiting penetration in tissue to only few millimetres. Visualisation of deeper anatomy is however critical for accurate assessment of plaque burden in-vivo. Methods: A compensation algorithm, previously developed to correct for light attenuation in soft tissues and to enhance contrast in ophthalmic OCT images, was applied to intracoronary plaque imaging using spectral-domain OCT. Results: Application of the compensation algorithm significantly increased tissue contrast in the vessel wall and atherosclerotic plaque boundaries. Contrast enhancement allows a better differentiation of plaque morphology, which is particularly important for the identification of lipid rich fibro atheromatous plaques and to guide decision on treatment strategy. Conclusion: The analysis of arterial vessel structure clinically captured with OCT is improved when used in conjunction with automated attenuation compensation. This approach may improve the OCT-based interpretation of coronary plaque morphology in clinical practice.

Recommendations for processing atmospheric attenuated backscatter profiles from Vaisala CL31 ceilometers

Science.gov (United States)

Kotthaus, Simone; O'Connor, Ewan; Münkel, Christoph; Charlton-Perez, Cristina; Haeffelin, Martial; Gabey, Andrew M.; Grimmond, C. Sue B.

2016-08-01

Ceilometer lidars are used for cloud base height detection, to probe aerosol layers in the atmosphere (e.g. detection of elevated layers of Saharan dust or volcanic ash), and to examine boundary layer dynamics. Sensor optics and acquisition algorithms can strongly influence the observed attenuated backscatter profiles; therefore, physical interpretation of the profiles requires careful application of corrections. This study addresses the widely deployed Vaisala CL31 ceilometer. Attenuated backscatter profiles are studied to evaluate the impact of both the hardware generation and firmware version. In response to this work and discussion within the CL31/TOPROF user community (TOPROF, European COST Action aiming to harmonise ground-based remote sensing networks across Europe), Vaisala released new firmware (versions 1.72 and 2.03) for the CL31 sensors. These firmware versions are tested against previous versions, showing that several artificial features introduced by the data processing have been removed. Hence, it is recommended to use this recent firmware for analysing attenuated backscatter profiles. To allow for consistent processing of historic data, correction procedures have been developed that account for artefacts detected in data collected with older firmware. Furthermore, a procedure is proposed to determine and account for the instrument-related background signal from electronic and optical components. This is necessary for using attenuated backscatter observations from any CL31 ceilometer. Recommendations are made for the processing of attenuated backscatter observed with Vaisala CL31 sensors, including the estimation of noise which is not provided in the standard CL31 output. After taking these aspects into account, attenuated backscatter profiles from Vaisala CL31 ceilometers are considered capable of providing valuable information for a range of applications including atmospheric boundary layer studies, detection of elevated aerosol layers, and model

A simulation of the optical attenuation of TPB coated light-guide detectors

International Nuclear Information System (INIS)

Jones, B J P

2013-01-01

This note is provided as a supplementary section to accompany the paper [1] which has been included in these proceedings. It describes some simple simulations which were performed in order to understand the attenuation behaviors of acrylic light-guides operated in air and argon, which were characterized in [2]. Whilst these simulations are only at the level of sophistication of a toy model, they illustrate interesting non-exponential light attenuation effects and the differences between operating light-guide based detectors in argon and air environments. We investigate the effects of surface absorption, surface roughness and wavelength dependence, and use a model tuned on the light-guide attenuation curve measured in air to make a prediction of the light-guide attenuation curve in argon. This curve is compared with data from a liquid argon test stand, and an improvement over a simple exponential model is observed

Prediction Method for Rain Rate and Rain Propagation Attenuation for K-Band Satellite Communications Links in Tropical Areas

Directory of Open Access Journals (Sweden)

Baso Maruddani

2015-01-01

Full Text Available This paper deals with the prediction method using hidden Markov model (HMM for rain rate and rain propagation attenuation for K-band satellite communication link at tropical area. As is well known, the K-band frequency is susceptible of being affected by atmospheric condition, especially in rainy condition. The wavelength of K-band frequency which approaches to the size of rain droplet causes the signal strength is easily attenuated and absorbed by the rain droplet. In order to keep the quality of system performance for K-band satellite communication link, therefore a special attention has to be paid for rain rate and rain propagation attenuation. Thus, a prediction method for rain rate and rain propagation attenuation based on HMM is developed to process the measurement data. The measured and predicted data are then compared with the ITU-R recommendation. From the result, it is shown that the measured and predicted data show similarity with the model of ITU-R P.837-5 recommendation for rain rate and the model of ITU-R P.618-10 recommendation for rain propagation attenuation. Meanwhile, statistical data for measured and predicted data such as fade duration and interfade duration have insignificant discrepancy with the model of ITU-R P.1623-1 recommendation.

Qing Dai attenuates nonsteroidal anti-inflammatory drug-induced mitochondrial reactive oxygen species in gastrointestinal epithelial cells.

Science.gov (United States)

Saito, Rie; Tamura, Masato; Matsui, Hirofumi; Nagano, Yumiko; Suzuki, Hideo; Kaneko, Tsuyoshi; Mizokami, Yuji; Hyodo, Ichinosuke

2015-01-01

Treatments with nonsteroidal anti-inflammatory drugs (NSAIDs) have increased the number of patients with gastrointestinal complications. Qing Dai has been traditionally used in Chinese herbal medicine for various inflammatory diseases such as ulcerative colitis. We previously reported that Qing Dai suppressed inflammations by scavenging reactive oxygen species (ROS) in ulcerative colitis patients. Thus, Qing Dai can attenuate the production of ROS, which play an important role in NSAID-induced gastrointestinal injuries. In this study, we aimed to elucidate whether Qing Dai decreased mitochondrial ROS production in NSAID-treated gastrointestinal cells by examining cellular injury, mitochondrial membrane potentials, and ROS production with specific fluorescent indicators. We also performed electron paramagnetic resonance measurement in isolated mitochondria with a spin-trapping reagent (CYPMPO or DMPO). Treatments with indomethacin and aspirin induced cellular injury and mitochondrial impairment in the gastrointestinal cells. Under these conditions, mitochondrial alterations were observed on electron microscopy. Qing Dai prevented these complications by suppressing ROS production in gastrointestinal cells. These results indicate that Qing Dai attenuated the ROS production from the NSAID-induced mitochondrial alteration in the gastrointestinal epithelial cells. Qing Dai treatment may be considered effective for the prevention NSAID-induced gastrointestinal injury.

A simple melatonin treatment protocol attenuates the response to acute stress in the sole Solea senegalensis

DEFF Research Database (Denmark)

Gesto, Manuel; Álvarez-Otero, Rosa; Conde-Sieira, Marta

2016-01-01

Several compounds have been tested in fish in order to attenuate the effects of different stressors, most often following previous observations in mammals. The hormone melatonin (MEL) and the amino acid L-tryptophan have been tested for this purpose with different degree of success. In Senegalese...... sole (Solea senegalensis) we have previously observed that during prolonged exposure to relatively mild stressors, the presence of MEL in the water helped to reduce the stress response. Here, we aimed to investigate the potential anti-stress effects of a short melatonin exposure that could be easily...... performed in fish farms before an intended manipulative event with the animals. Our results demonstrate that adding MEL to the tanks 30. min before an acute chasing stress is effective in reducing the intensity of the stress response in fish from its beginning, as evidenced by the attenuated and delayed...

Indirect measure of X-rays spectra using TLDs; Medicion indirecta de espectros de rayos X utilizando TLDs

Energy Technology Data Exchange (ETDEWEB)

Bonzi, E. V.; Mainardi, R. T. [Universidad Nacional de Cordoba, Facultad de Matematica, Astronomia y Fisica, Av. Haya de la Torre y Av. Medina Allende s/n, Ciudad Universitaria, X5016LEA Cordoba (Argentina)

2011-10-15

A methodology of indirect measure of X-rays spectra, emitted by conventional tubes, was developed recently and its feasibility verified in the first place by Monte Carlo simulations. For that case is intended to measure, by means of plastic scintillators, attenuation curves of dispersed beams previously. In this work were carried out measurements of attenuation curves with thermoluminescent dosimeters (TLD) to verify the kindness of the indirect measure method. The attenuation curve was also measured using an ionization chamber brand Capintec (model 192) with the purpose of making a comparison. The results of the attenuation curve measured with both dosimeters present a good resolution inside the statistical fluctuations and the spectral reconstruction using diverse parametric functions is carried out in a quick and simple way with excellent resolutions in the functional form. For this reconstruction method are of fundamental importance the following properties of the used dosimeter: in the first place the repetition of the measures, property that could check; in second place the precision of the measured data and lastly the dosimeter response, this is, the increase of the thermoluminescent signal before an increase of the photons flow of X-rays. This parameter is the gradient of the curve thermoluminescent signal versus the dose imparted to the dosimeter. The measures were realized with a generator of X-rays brand Kevex provided of a conventional tube with tungsten anti cathode that polarizes with high tension to a maximum value of 50 kV and current of 0.5 ma. (Author)

Ground-Based Radiometric Measurements of Slant Path Attenuation in the V/W Bands

Science.gov (United States)

2016-04-01

the drawings, specifications, or other data does not license the holder or any other person or corporation; or convey any rights or permission to...atmosphere were used to generate the attenuation retrieval algorithm. 15. SUBJECT TERMS Radio wave propagation, remote sensing, instruments and techniques...Predicting antenna noise temperature due to rain clouds at microwave and millimeter- wave frequencies,” IEEE Trans. Antennas and Propagat., vol. 55, n. 7

Virtual non-contrast in second-generation, dual-energy computed tomography: Reliability of attenuation values

International Nuclear Information System (INIS)

Toepker, Michael; Moritz, Thomas; Krauss, Bernhard; Weber, Michael; Euller, Gordon; Mang, Thomas; Wolf, Florian; Herold, Christian J.; Ringl, Helmut

2012-01-01

Purpose: To evaluate the reliability of attenuation values in virtual non-contrast images (VNC) reconstructed from contrast-enhanced, dual-energy scans performed on a second-generation dual-energy CT scanner, compared to single-energy, non-contrast images (TNC). Materials and methods: Sixteen phantoms containing a mixture of contrast agent and water at different attenuations (0–1400 HU) were investigated on a Definition Flash-CT scanner using a single-energy scan at 120 kV and a DE-CT protocol (100 kV/SN140 kV). For clinical assessment, 86 patients who received a dual-phase CT, containing an unenhanced single-energy scan at 120 kV and a contrast enhanced (110 ml Iomeron 400 mg/ml; 4 ml/s) DE-CT (100 kV/SN140 kV) in an arterial (n = 43) or a venous phase, were retrospectively analyzed. Mean attenuation was measured within regions of interest of the phantoms and in different tissue types of the patients within the corresponding VNC and TNC images. Paired t-tests and Pearson correlation were used for statistical analysis. Results: For all phantoms, mean attenuation in VNC was 5.3 ± 18.4 HU, with respect to water. In 86 patients overall, 2637 regions were measured in TNC and VNC images, with a mean difference between TNC and VNC of −3.6 ± 8.3 HU. In 91.5% (n = 2412) of all cases, absolute differences between TNC and VNC were under 15 HU, and, in 75.3% (n = 1986), differences were under 10 HU. Conclusions: Second-generation dual-energy CT based VNC images provide attenuation values close to those of TNC. To avoid possible outliers multiple measurements are recommended especially for measurements in the spleen, the mesenteric fat, and the aorta.

Virtual non-contrast in second-generation, dual-energy computed tomography: reliability of attenuation values.

Science.gov (United States)

Toepker, Michael; Moritz, Thomas; Krauss, Bernhard; Weber, Michael; Euller, Gordon; Mang, Thomas; Wolf, Florian; Herold, Christian J; Ringl, Helmut

2012-03-01

To evaluate the reliability of attenuation values in virtual non-contrast images (VNC) reconstructed from contrast-enhanced, dual-energy scans performed on a second-generation dual-energy CT scanner, compared to single-energy, non-contrast images (TNC). Sixteen phantoms containing a mixture of contrast agent and water at different attenuations (0-1400 HU) were investigated on a Definition Flash-CT scanner using a single-energy scan at 120 kV and a DE-CT protocol (100 kV/SN140 kV). For clinical assessment, 86 patients who received a dual-phase CT, containing an unenhanced single-energy scan at 120 kV and a contrast enhanced (110 ml Iomeron 400 mg/ml; 4 ml/s) DE-CT (100 kV/SN140 kV) in an arterial (n=43) or a venous phase, were retrospectively analyzed. Mean attenuation was measured within regions of interest of the phantoms and in different tissue types of the patients within the corresponding VNC and TNC images. Paired t-tests and Pearson correlation were used for statistical analysis. For all phantoms, mean attenuation in VNC was 5.3±18.4 HU, with respect to water. In 86 patients overall, 2637 regions were measured in TNC and VNC images, with a mean difference between TNC and VNC of -3.6±8.3 HU. In 91.5% (n=2412) of all cases, absolute differences between TNC and VNC were under 15HU, and, in 75.3% (n=1986), differences were under 10 HU. Second-generation dual-energy CT based VNC images provide attenuation values close to those of TNC. To avoid possible outliers multiple measurements are recommended especially for measurements in the spleen, the mesenteric fat, and the aorta. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Computer-controlled attenuator.

Science.gov (United States)

Mitov, D; Grozev, Z

1991-01-01

Various possibilities for applying electronic computer-controlled attenuators for the automation of physiological experiments are considered. A detailed description is given of the design of a 4-channel computer-controlled attenuator, in two of the channels of which the output signal can change by a linear step, in the other two channels--by a logarithmic step. This, together with the existence of additional programmable timers, allows to automate a wide range of studies in different spheres of physiology and psychophysics, including vision and hearing.

Caffeine attenuates scopolamine-induced memory impairment in humans.

Science.gov (United States)

Riedel, W; Hogervorst, E; Leboux, R; Verhey, F; van Praag, H; Jolles, J

1995-11-01

Caffeine consumption can be beneficial for cognitive functioning. Although caffeine is widely recognized as a mild CNS stimulant drug, the most important consequence of its adenosine antagonism is cholinergic stimulation, which might lead to improvement of higher cognitive functions, particularly memory. In this study, the scopolamine model of amnesia was used to test the cholinergic effects of caffeine, administered as three cups of coffee. Subjects were 16 healthy volunteers who received 250 mg caffeine and 2 mg nicotine separately, in a placebo-controlled double-blind cross-over design. Compared to placebo, nicotine attenuated the scopolamine-induced impairment of storage in short-term memory and attenuated the scopolamine-induced slowing of speed of short-term memory scanning. Nicotine also attenuated the scopolamine-induced slowing of reaction time in a response competition task. Caffeine attenuated the scopolamine-induced impairment of free recall from short- and long-term memory, quality and speed of retrieval from long-term memory in a word learning task, and other cognitive and non-cognitive measures, such as perceptual sensitivity in visual search, reading speed, and rate of finger-tapping. On the basis of these results it was concluded that caffeine possesses cholinergic cognition enhancing properties. Caffeine could be used as a control drug in studies using the scopolamine paradigm and possibly also in other experimental studies of cognitive enhancers, as the effects of a newly developed cognition enhancing drug should at least be superior to the effects of three cups of coffee.

Seismic High Attenuation Beneath Southern New England Indicates High Asthenospheric Temperature and No Melt

Science.gov (United States)

Dong, M. T.; Menke, W. H.

2017-12-01

Seismic attenuation exhibits strong geographic variability in northeastern North America, with the highest values associated with the previously-recognized Northern Appalachian Anomaly (NAA) in southern New England. The shear wave quality factor at 100 km depth is 14sNAA, possibly due to lithospheric delamination caused by directional asthenospheric flow.

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

Science.gov (United States)

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

2015-03-03

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

Ultrasonic attenuation in the superconducting and intermediate states of pure and doped type I superconductors

International Nuclear Information System (INIS)

Chaudhuri, K.D.; Singh, R.

1982-01-01

The attenuation of longitudinal ultrasonic waves has been measured in single crystals of indium (99.999%), indium doped with 0.003 at % of tin, and indium doped with 0.002 at % of bismuth in the intermediate and superconducting states over the frequency range 10--30 MHz. For the bismuth-doped indium specimen, measurements were taken for three different physical states, i.e., for three different dislocation densities, and for the indium and the tin-doped indium specimens, measurements were for one-physical state. For a particular measurement, the same physical state was maintained both in the intermediate and superconducting states. A temperature-dependent oscillatory behavior of the ultrasonic attenuation was observed in the intermediate state in all the three specimens, but in the superconducting state the oscillatory behavior was observed only in the bismuth-doped specimen. Two phases have been identified in the superconducting layers of the intermediate state and there is only one phase in the superconducting state of the bismuth-doped sample. The origin of the two phases in the intermediate state and that of the single phase in the superconducting state of the bismuth-doped sample are discussed. A qualitative explanation is presented for the occurrence of oscillatory attenuation in the intermediate state irrespective of the nature of the dopant and the selective occurrence of oscillatory attenuation in the superconducting state due to the nature of the dopant

Utilisation of ISA Reverse Genetics and Large-Scale Random Codon Re-Encoding to Produce Attenuated Strains of Tick-Borne Encephalitis Virus within Days.

Science.gov (United States)

de Fabritus, Lauriane; Nougairède, Antoine; Aubry, Fabien; Gould, Ernest A; de Lamballerie, Xavier

2016-01-01

Large-scale codon re-encoding is a new method of attenuating RNA viruses. However, the use of infectious clones to generate attenuated viruses has inherent technical problems. We previously developed a bacterium-free reverse genetics protocol, designated ISA, and now combined it with large-scale random codon-re-encoding method to produce attenuated tick-borne encephalitis virus (TBEV), a pathogenic flavivirus which causes febrile illness and encephalitis in humans. We produced wild-type (WT) and two re-encoded TBEVs, containing 273 or 273+284 synonymous mutations in the NS5 and NS5+NS3 coding regions respectively. Both re-encoded viruses were attenuated when compared with WT virus using a laboratory mouse model and the relative level of attenuation increased with the degree of re-encoding. Moreover, all infected animals produced neutralizing antibodies. This novel, rapid and efficient approach to engineering attenuated viruses could potentially expedite the development of safe and effective new-generation live attenuated vaccines.

Ultrasound fields in an attenuating medium

DEFF Research Database (Denmark)

Jensen, Jørgen Arendt; Gandhi,, D; O'Brien,, W.D., Jr.

1993-01-01

of the rectangles and sums all contributions to arrive at the spatial impulse response for the aperture and field point. This approach makes it possible to model all transducer apertures, and the program can readily calculate the emitted, pulse-echo and continuous wave field. Attenuation is included by splitting...... it into a frequency dependent part and frequency independent part. The latter results in an attenuation factor that is multiplied onto the responses from the individual elements, and the frequency dependent part is handled by attenuating the basic one-dimensional pulse. The influence on ultrasound fields from......Ultrasound fields propagating in tissue will undergo changes in shape not only due to diffraction, but also due to the frequency dependent attenuation. Linear fields can be fairly well predicted for a non-attenuating medium like water by using the Tupholme-Stepanishen method for calculating...

Indomethacin attenuation of radiation-induced hyperthermia does not modify radiation-induced motor hypoactivity

Energy Technology Data Exchange (ETDEWEB)

Ferguson, J.L.; Kandasamy, S.B.; Harris, A.H.; Davis, H.D.; Landauer, M.R. [Armed Forces Radiobiology Research Inst., Bethesda, MD (United States)

1996-09-01

Exposure of rats to 5-10 Gy of ionizing radiation produces hyperthermia and reduces motor activity. Previous studies suggested that radiation-induced hyperthermia results from a relatively direct action on the brain and is mediated by prostaglandins. To test the hypothesis that hypoactivity may be, in part, a thermoregulatory response to this elevation in body temperature, adult male rats were given indomethacin (0.0, 0.5, 1.0, and 3.0 mg/kg, intraperitoneally), a blocker of prostaglandin synthesis, and were either irradiated (LINAC 18.6 MeV (nominal) high-energy electrons, 10 Gy at 10 Gy/min, 2.8 {mu}sec pulses at 2 Hz) or sham-irradiated. The locomotor activity of all rats was then measured for 30 min in a photocell monitor for distance traveled and number of vertical movements. Rectal temperatures of irradiated rats administered vehicle only were elevated by 0.9{+-}0.2degC at the beginning and the end of the activity session. Although indomethacin, at the two higher doses tested, attenuated the hyperthermia in irradiated rats by 52-75%, it did not attenuate radiation-induced reductions in motor activity. These results indicate that motor hypoactivity after exposure to 10 Gy of high-energy electrons is not due to elevated body temperature or to the increased synthesis of prostaglandins. (author)

Indomethacin attenuation of radiation-induced hyperthermia does not modify radiation-induced motor hypoactivity

International Nuclear Information System (INIS)

Ferguson, J.L.; Kandasamy, S.B.; Harris, A.H.; Davis, H.D.; Landauer, M.R.

1996-01-01

Exposure of rats to 5-10 Gy of ionizing radiation produces hyperthermia and reduces motor activity. Previous studies suggested that radiation-induced hyperthermia results from a relatively direct action on the brain and is mediated by prostaglandins. To test the hypothesis that hypoactivity may be, in part, a thermoregulatory response to this elevation in body temperature, adult male rats were given indomethacin (0.0, 0.5, 1.0, and 3.0 mg/kg, intraperitoneally), a blocker of prostaglandin synthesis, and were either irradiated (LINAC 18.6 MeV (nominal) high-energy electrons, 10 Gy at 10 Gy/min, 2.8 μsec pulses at 2 Hz) or sham-irradiated. The locomotor activity of all rats was then measured for 30 min in a photocell monitor for distance traveled and number of vertical movements. Rectal temperatures of irradiated rats administered vehicle only were elevated by 0.9±0.2degC at the beginning and the end of the activity session. Although indomethacin, at the two higher doses tested, attenuated the hyperthermia in irradiated rats by 52-75%, it did not attenuate radiation-induced reductions in motor activity. These results indicate that motor hypoactivity after exposure to 10 Gy of high-energy electrons is not due to elevated body temperature or to the increased synthesis of prostaglandins. (author)

Diffuse Attenuation Coef. K490, Aqua MODIS, 0.125 degrees, Indonesia

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — OSU distributes Diffuse Attenuation Coefficient at 490 nm Wavelength data from NASA's Aqua satellite. Measurements are gathered by the Moderate Resolution Imaging...

Characterization of the relation between CT technical parameters and accuracy of quantification of lung attenuation on quantitative chest CT.

Science.gov (United States)

Trotta, Brian M; Stolin, Alexander V; Williams, Mark B; Gay, Spencer B; Brody, Alan S; Altes, Talissa A

2007-06-01

The purpose of this study was to assess the compromise between CT technical parameters and the accuracy of CT quantification of lung attenuation. Materials that simulate water (0 H), healthy lung (-650 H), borderline emphysematous lung (-820 H), and severely emphysematous lung (-1,000 H) were placed at both the base and the apex of the lung of an anthropomorphic phantom and outside the phantom. Transaxial CT images through the samples were obtained while the effective tube current was varied from 440 to 10 mAs, kilovoltage from 140 to 80 kVp, and slice thickness from 0.625 to 10 mm. Mean +/- SD attenuation within the samples and the standard quantitative chest CT measurements, the percentage of pixels with attenuation less than -910 H and 15th percentile of attenuation, were computed. Outside the phantom, variations in CT parameters produced less than 2.0% error in all measurements. Within the anthropomorphic phantom at 30 mAs, error in measurements was much larger, ranging from zero to 200%. Below approximately 80 mAs, mean attenuation became increasingly biased. The effects were most pronounced at the apex of the lungs. Mean attenuation of the borderline emphysematous sample of apex decreased 55 H as the tube current was decreased from 300 to 30 mAs. Both the 15th percentile of attenuation and percentage of pixels with less than -910 H attenuation were more sensitive to variations in effective tube current than was mean attenuation. For example, the -820 H sample should have 0% of pixels less than -910 H, which was true at 400 mA. At 30 mA in the lung apex, however, the measurement was highly inaccurate, 51% of pixels being below this value. Decreased kilovoltage and slice thickness had analogous, but lesser, effects. The accuracy of quantitative chest CT is determined by the CT acquisition parameters. There can be significant decreases in accuracy at less than 80 mAs for thin slices in an anthropomorphic phantom, the most pronounced effects occurring in the lung

Detection and measurement of gamma-ray self-attenuation in plutonium residues

International Nuclear Information System (INIS)

Prettyman, T.H.; Foster, L.A.; Estep, R.J.

1996-01-01

A new method to correct for self-attenuation in gamma-ray assays of plutonium is presented. The underlying assumptions of the technique are based on a simple but accurate physical model of plutonium residues, particularly pyrochemical salts, in which it is assumed that the plutonium is divided into two portions, each of which can be treated separately from the standpoint of gamma-ray analysis: a portion that is in the form of plutonium metal shot; and a dilute portion that is mixed with the matrix. The performance of the technique is evaluated using assays of plutonium residues by tomographic gamma scanning at the Los Alamos Plutonium Facility. The ability of the method to detect saturation conditions is examined

Attenuation in Superconducting Circular Waveguides

Directory of Open Access Journals (Sweden)

K. H. Yeap

2016-09-01

Full Text Available We present an analysis on wave propagation in superconducting circular waveguides. In order to account for the presence of quasiparticles in the intragap states of a superconductor, we employ the characteristic equation derived from the extended Mattis-Bardeen theory to compute the values of the complex conductivity. To calculate the attenuation in a circular waveguide, the tangential fields at the boundary of the wall are first matched with the electrical properties (which includes the complex conductivity of the wall material. The matching of fields with the electrical properties results in a set of transcendental equations which is able to accurately describe the propagation constant of the fields. Our results show that although the attenuation in the superconducting waveguide above cutoff (but below the gap frequency is finite, it is considerably lower than that in a normal waveguide. Above the gap frequency, however, the attenuation in the superconducting waveguide increases sharply. The attenuation eventually surpasses that in a normal waveguide. As frequency increases above the gap frequency, Cooper pairs break into quasiparticles. Hence, we attribute the sharp rise in attenuation to the increase in random collision of the quasiparticles with the lattice structure.

Radiofrequency attenuator and method

Science.gov (United States)

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.

Moisture profile measurements of concrete samples in vertical flow by gamma ray attenuation method. Medidas do perfil de umidade de amostras de concreto em infiltracao vertical, atraves da atenuacao de raios gama

Energy Technology Data Exchange (ETDEWEB)

Appoloni, C R; Nardocci, A C; Obuti, M M [Universidade Estadual de Londrina, PR (Brazil). Dept. de Fisica

1988-04-01

This work deals with the study of the water diffusion in concrete by the gamma ray attenuation method. The moisture profiles, [theta] (z,t), of the vertical water flow were determined in concrete samples of different trace and porosity. The data were taken with a vertical and horizontal measurement table, a [sup 60] Co gamma ray source, a NaI (T) scintillation detector and the standard gamma ray spectrometry electronic. The [theta] (z,t) data analysis is presented using a phenomenological model of the moisture profile temporal evolution in heterogeneous materials. Two other models, Cell and Sandwich, were also applied to determine the attenuation coefficient of a non-homogeneous media from the attenuation coefficients of the components, taking into account particles-size effects. (author).

Assessment of endothelial function and myocardial flow reserve using {sup 15}O-water PET without attenuation correction

Energy Technology Data Exchange (ETDEWEB)

Tuffier, Stephane; Joubert, Michael; Bailliez, Alban [EA 4650, Normandie Universite, Caen (France); Legallois, Damien [EA 4650, Normandie Universite, Caen (France); Caen University Hospital, Department of Cardiology, Caen (France); Belin, Annette [Caen University Hospital, Department of Cardiac Surgery, Caen (France); Redonnet, Michel [Rouen University Hospital, Department of Cardiac Surgery, Rouen (France); Agostini, Denis [EA 4650, Normandie Universite, Caen (France); Caen University Hospital, Department of Nuclear Medicine, Caen (France); Manrique, Alain [EA 4650, Normandie Universite, Caen (France); Caen University Hospital, Department of Nuclear Medicine, Caen (France); Cyceron PET Centre, Caen (France)

2016-02-15

Myocardial blood flow (MBF) measurement using positron emission tomography (PET) from the washout rate of {sup 15}O-water is theoretically independent of tissue attenuation. The aim of this study was to evaluate the impact of not using attenuation correction in the assessment of coronary endothelial function and myocardial flow reserve (MFR) using {sup 15}O-water PET. We retrospectively processed 70 consecutive {sup 15}O-water PET examinations obtained at rest and during cold pressor testing (CPT) in patients with dilated cardiomyopathy (n = 58), or at rest and during adenosine infusion in heart transplant recipients (n = 12). Data were reconstructed with attenuation correction (AC) and without attenuation correction (NAC) using filtered backprojection, and MBF was quantified using a single compartmental model. The agreement between AC and NAC data was assessed using Lin's concordance correlation coefficient followed by Bland-Altman plot analysis. Regarding endothelial function, NAC PET showed poor reproducibility and poor agreement with AC PET data. Conversely, NAC PET demonstrated high reproducibility and a strong agreement with AC PET for the assessment of MFR. Non-attenuation-corrected {sup 15}O-water PET provided an accurate measurement of MFR compared to attenuation-corrected PET. However, non-attenuation-corrected PET data were less effective for the assessment of endothelial function using CPT in this population. (orig.)

Rotavirus specific plasma secretory immunoglobulin in children with acute gastroenteritis and children vaccinated with an attenuated human rotavirus vaccine

Science.gov (United States)

Herrera, Daniel; Vásquez, Camilo; Corthésy, Blaise; Franco, Manuel A; Angel, Juana

2013-01-01

Rotavirus (RV)–specific secretory immunoglobulin (RV-SIg) has been previously detected in serum of naturally RV infected children and shown to reflect the intestinal Ig immune response. Total plasma SIgA and plasma RV-SIg were evaluated by ELISA in children with gastroenteritis due or not due to RV infection and in 50 children vaccinated with the attenuated RIX4414 human RV vaccine and 62 placebo recipients. RV-SIg was only detected in children with evidence of previous RV infection or with acute RV gastroenteritis. Vaccinees had higher RV-SIg titers than placebo recipients and RV-SIg titers increased after the second vaccine dose. RV-SIg measured after the second dose correlated with protection when vaccinees and placebo recipients were analyzed jointly. RV-SIg may serve as a valuable correlate of protection for RV vaccines. PMID:23839157

Chlorine isotope investigation of natural attenuation of trichloroethene in an aerobic aquifer

International Nuclear Information System (INIS)

Sturchio, N.C.; Heraty, L.J.; Huang, L.; Holt, B.D.; Abrajano, T.A. Jr.; Clausen, J.L.

1998-01-01

Natural attenuation of chlorinated aliphatic hydrocarbons (CAHs) can be an important mechanism for groundwater remediation. It is difficult to determine the effectiveness of natural CAH attenuation from chemical analyses of groundwater samples because mixing, dispersion, and secondary reactions can mask the chemical evidence of attenuation. In this paper, the authors explore the application of stable chlorine isotope ratio measurements as a new tool for evaluating natural attenuation of CAHs. They report stable isotope ratios of chlorine in both trichloroethene (TCE) and inorganic chloride in groundwater from an aerobic aquifer beneath an extensively contaminated industrial site, the Paducah Gaseous Diffusion Plant in western Kentucky. Variations in the concentrations and chlorine isotope ratios of TCE and chloride in the groundwater are consistent with those expected from natural attenuation. These data support a model in which partial TCE degradation occurred in relatively impermeable, clay-rich sediments above the aquifer, and little or no further degradation of TCE occurred within the aquifer. A record of changing conditions within the TCE source area can be inferred from the spatial variation of chlorine isotope ratios for TCE and chloride within the plume

Chemical Oxygen Demand (COD) Attenuation of Methyl Red in ...

African Journals Online (AJOL)

ADOWIE PERE

Department of Pure & Industrial Chemistry, Faculty of Science , University of ... ABSTRACT: Attenuation of methyl red dyestuff in water was assessed by ... alternative low cost materials (Ahmad et al., 2010, .... ml distilled water as blank was also taken through the .... quality control measures such as washing of glassware,.

Phonic Attenuation due to Screen-Barriers

Directory of Open Access Journals (Sweden)

Vasile Bacria

2011-10-01

Full Text Available The technique of noise decreasing admits two basic approaches: an active approach and a passive one. In the frame of passive method one can count the employment of screen-barriers. In this paper we present some considerations on sound attenuation due to screen-barriers emphasizing the elements which influence it. The elucidation of these elements is made by measurements. The obtained results can be applied in every other practical situation concerning the protection against noise.

Scatter and attenuation correction in SPECT

International Nuclear Information System (INIS)

Ljungberg, Michael

2004-01-01

The adsorbed dose is related to the activity uptake in the organ and its temporal distribution. Measured count rate with scintillation cameras is related to activity through the system sensitivity, cps/MBq. By accounting for physical processes and imaging limitations we can measure the activity at different time points. Correction for physical factor, such as attenuation and scatter is required for accurate quantitation. Both planar and SPECT imaging can be used to estimate activities for radiopharmaceutical dosimetry. Planar methods have been the most widely used but is a 2D technique. With accurate modelling for imagine in iterative reconstruction, SPECT methods will prove to be more accurate

Initial evaluation of ultrasonic attenuation measurements for estimating fracture toughness of RPV steels

Energy Technology Data Exchange (ETDEWEB)

Hiser, A.L. Jr.; Green, R.E. Jr. [Johns Hopkins Univ., Baltimore, MD (United States). Center for Nondestructive Evaluation

1999-08-01

Neutron bombardment of reactor pressure vessel (RPV) steels causes reductions in fracture toughness in these steels, termed neutron irradiation embrittlement. Currently, there are no accepted methods for nondestructive determination of the extent of the irradiation embrittlement nor the actual fracture toughness of the reactor pressure vessel. This paper provides initial results of an effort addressing the use of ultrasonic attenuation as a suitable parameter for nondestructive determination of irradiation embrittlement in RPV steels. (orig.)

Calibration of Recoil-In-Vacuum attenuations from first principles: comparison with recent experimental data on Fe isotopes

International Nuclear Information System (INIS)

Stone, Nicholas James; Stone, Jirina Rikovska; Stuchbery, Andrew E.; Jonsson, Per

2015-01-01

Precession of aligned nuclear spin systems in ions recoiling from the target into vacuum (RIV) with consequent attenuation of angular distributions of emitted radiation is, in principle, a versatile method for measurement of g-factors of nuclear excited states of lifetimes in the pico-second range (Stone et al., Phys. Rev. Lett., 94, 192501, 2005 and Stuchbery and Stone, Phys. Rev. C, 76, 034307, 2007). Calibration of the observed attenuations has been achieved in favourable cases through comparison with measurements on states having previously known g-factors and lifetimes. The general lack of suitable states with known g-factors has limited application of the RIV method. This paper concerns the present status of efforts to describe the states of excited ions recoiling into vacuum in detail so that the average interaction can be estimated with useful precision from a-priori theory. The calculations use the GRASP2K package (Froese-Fischer et al. 1997 and Jonsson, Comp. Phys. Comm., 177, 597, 2007 & 184, 2197, 2013) to obtain, for each recoiling ion change state, the individual possible electronic states, their configurations, lifetimes and hyperfine interactions. It is assumed that all possible ionic states are produced, up to a chosen excitation energy. This energy is selected to approximate the energy at which all states have lifetimes far shorter than the nuclear state of interest. It is further assumed that the ionic state total electron angular momenta are randomly oriented in space. The first estimates of the average attenuation of emission distributions, as a function of the product g τ of the nuclear state g-factor and mean lifetime, used an averaged precession frequency obtained neglecting transitions between electronic states. Improved calculations, which include such transitions, are described

Signal Attenuation Curve for Different Surface Detector Arrays

Science.gov (United States)

Vicha, J.; Travnicek, P.; Nosek, D.; Ebr, J.

2014-06-01

Modern cosmic ray experiments consisting of large array of particle detectors measure the signals of electromagnetic or muon components or their combination. The correction for an amount of atmosphere passed is applied to the surface detector signal before its conversion to the shower energy. Either Monte Carlo based approach assuming certain composition of primaries or indirect estimation using real data and assuming isotropy of arrival directions can be used. Toy surface arrays of different sensitivities to electromagnetic and muon components are assumed in MC simulations to study effects imposed on attenuation curves for varying composition or possible high energy anisotropy. The possible sensitivity of the attenuation curve to the mass composition is also tested for different array types focusing on a future apparatus that can separate muon and electromagnetic component signals.

The LCLS Gas Attenuator Revisited

International Nuclear Information System (INIS)

Ryutov, D

2005-01-01

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 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 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 are

Is a picture worth a thousand words? The interaction of visual display and attribute representation in attenuating framing bias}

OpenAIRE

Eyal Gamliel; Hamutal Kreiner

2013-01-01

The attribute framing bias is a well-established phenomenon, in which an object or an event is evaluated more favorably when presented in a positive frame such as ``the half full glass'' than when presented in the complementary negative framing. Given that previous research showed that visual aids can attenuate this bias, the current research explores the factors underlying the attenuating effect of visual aids. In a series of three experiments, we examined how attribute framing bias is affec...

Interpersonal sensitivity and persistent attenuated psychotic symptoms in adolescence.

Science.gov (United States)

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

2018-03-01

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.

Experimental Test of a New Precision Model for Microwave Rotary Vane Attenuators

DEFF Research Database (Denmark)

Guldbrandsen, Tom; Guldbrandsen, Birthe; Warner, Frank L.

1983-01-01

coefficients have been measured versus angle of rotation by means of a computer-corrected automatic network analyzer and, within the uncertainty, they agree with the model. From the reflection measurements, corrections to the attenuation were calculated using relations derived from the model. The corrections...

Maximum likelihood estimation of the attenuated ultrasound pulse

DEFF Research Database (Denmark)

Rasmussen, Klaus Bolding

1994-01-01

The attenuated ultrasound pulse is divided into two parts: a stationary basic pulse and a nonstationary attenuation pulse. A standard ARMA model is used for the basic pulse, and a nonstandard ARMA model is derived for the attenuation pulse. The maximum likelihood estimator of the attenuated...

Holdup measurements under realistic conditions

International Nuclear Information System (INIS)

Sprinkel, J.K. Jr.; Marshall, R.; Russo, P.A.; Siebelist, R.

1997-01-01

This paper reviews the documentation of the precision and bias of holdup (residual nuclear material remaining in processing equipment) measurements and presents previously unreported results. Precision and bias results for holdup measurements are reported from training seminars with simulated holdup, which represent the best possible results, and compared to actual plutonium processing facility measurements. Holdup measurements for plutonium and uranium processing plants are also compared to reference values. Recommendations for measuring holdup are provided for highly enriched uranium facilities and for low enriched uranium facilities. The random error component of holdup measurements is less than the systematic error component. The most likely factor in measurement error is incorrect assumptions about the measurement, such as background, measurement geometry, or signal attenuation. Measurement precision on the order of 10% can be achieved with some difficulty. Bias of poor quality holdup measurement can also be improved. However, for most facilities, holdup measurement errors have no significant impact on inventory difference, sigma, or safety (criticality, radiation, or environmental); therefore, it is difficult to justify the allocation of more resources to improving holdup measurements. 25 refs., 10 tabs

Comparative genomic analyses of Mycoplasma hyopneumoniae pathogenic 168 strain and its high-passaged attenuated strain

Science.gov (United States)

2013-01-01

Background Mycoplasma hyopneumoniae is the causative agent of porcine enzootic pneumonia (EP), a mild, chronic pneumonia of swine. Despite presenting with low direct mortality, EP is responsible for major economic losses in the pig industry. To identify the virulence-associated determinants of M. hyopneumoniae, we determined the whole genome sequence of M. hyopneumoniae strain 168 and its attenuated high-passage strain 168-L and carried out comparative genomic analyses. Results We performed the first comprehensive analysis of M. hyopneumoniae strain 168 and its attenuated strain and made a preliminary survey of coding sequences (CDSs) that may be related to virulence. The 168-L genome has a highly similar gene content and order to that of 168, but is 4,483 bp smaller because there are 60 insertions and 43 deletions in 168-L. Besides these indels, 227 single nucleotide variations (SNVs) were identified. We further investigated the variants that affected CDSs, and compared them to reported virulence determinants. Notably, almost all of the reported virulence determinants are included in these variants affected CDSs. In addition to variations previously described in mycoplasma adhesins (P97, P102, P146, P159, P216, and LppT), cell envelope proteins (P95), cell surface antigens (P36), secreted proteins and chaperone protein (DnaK), mutations in genes related to metabolism and growth may also contribute to the attenuated virulence in 168-L. Furthermore, many mutations were located in the previously described repeat motif, which may be of primary importance for virulence. Conclusions We studied the virulence attenuation mechanism of M. hyopneumoniae by comparative genomic analysis of virulent strain 168 and its attenuated high-passage strain 168-L. Our findings provide a preliminary survey of CDSs that may be related to virulence. While these include reported virulence-related genes, other novel virulence determinants were also detected. This new information will form

The attenuation of seismic intensity in the Etna region and comparison with other Italian volcanic districts

Directory of Open Access Journals (Sweden)

T. Tuvè

2006-06-01

Full Text Available A detailed analysis of the intensity attenuation in the Etna and other Italian volcanic districts, was performed using the most recent and complete intensity datasets. Attenuation laws were derived through empirical models fitting ?I (the difference between epicentral I0 and site Ix intensities average values versus hypocentral site distances by the least-square method. The huge amount of data available for the Etna area allowed us to elaborate bi-linear and logarithmic attenuation models, also taking source effects into account. Furthermore, the coefficients of the Grandori formulation have been re-calculated to verify the ones previously defined for seismic hazard purposes. Among the tested relationships, the logarithmic one is simple and fairly stable, so it was also adopted for the other volcanic Italian areas. The analysis showed different attenuation trends: on the one hand, Etna and Ischia show the highest decay of intensity (?I=4 in the first 20 km; on the contrary, the Aeolian Islands and Albani Hills present a slight intensity attenuation (?I=2 at 20 km from the hypocentre; finally, Vesuvius seems to have an intermediate behaviour between the two groups. The proposed regionalization gives a significantly better image of near-field damage in volcanic regions and is easily applicable to probabilistic seismic hazard analyses.

Attenuation correction for flexible magnetic resonance coils in combined magnetic resonance/positron emission tomography imaging.

Science.gov (United States)

Eldib, Mootaz; Bini, Jason; Calcagno, Claudia; Robson, Philip M; Mani, Venkatesh; Fayad, Zahi A

2014-02-01

Attenuation correction for magnetic resonance (MR) coils is a new challenge that came about with the development of combined MR and positron emission tomography (PET) imaging. This task is difficult because such coils are not directly visible on either PET or MR acquisitions with current combined scanners and are therefore not easily localized in the field of view. This issue becomes more evident when trying to localize flexible MR coils (eg, cardiac or body matrix coil) that change position and shape from patient to patient and from one imaging session to another. In this study, we proposed a novel method to localize and correct for the attenuation and scatter of a flexible MR cardiac coil, using MR fiducial markers placed on the surface of the coil to allow for accurate registration of a template computed tomography (CT)-based attenuation map. To quantify the attenuation properties of the cardiac coil, a uniform cylindrical water phantom injected with 18F-fluorodeoxyglucose (18F-FDG) was imaged on a sequential MR/PET system with and without the flexible cardiac coil. After establishing the need to correct for the attenuation of the coil, we tested the feasibility of several methods to register a precomputed attenuation map to correct for the attenuation. To accomplish this, MR and CT visible markers were placed on the surface of the cardiac flexible coil. Using only the markers as a driver for registration, the CT image was registered to the reference image through a combination of rigid and deformable registration. The accuracy of several methods was compared for the deformable registration, including B-spline, thin-plate spline, elastic body spline, and volume spline. Finally, we validated our novel approach both in phantom and patient studies. The findings from the phantom experiments indicated that the presence of the coil resulted in a 10% reduction in measured 18F-FDG activity when compared with the phantom-only scan. Local underestimation reached 22% in

Attenuation studies near K-absorption edges using Compton scattered 241Am gamma rays

International Nuclear Information System (INIS)

Abdullah, K.K.; Ramachandran, N.; Karunakaran Nair, K.; Babu, B.R.S.; Joseph, Antony; Thomas, Rajive; Varier, K.M.

2008-01-01

We have carried out photon attenuation measurements at several energies in the range from 49.38 keV to 57.96 keV around the K-absorption edges of the rare earth elements Sm, Eu, Gd, Tb, Dy and Er using 59.54 keV gamma rays from 241 Am source after Compton scattering from an aluminium target. Pellets of oxides of the rare earth elements were chosen as mixture absorbers in these investigations. A narrow beam good geometry set-up was used for the attenuation measurements. The scattered gamma rays were detected by an HPGe detector. The results are consistent with theoretical values derived from the XCOM package. (author)

Compensation for nonuniform attenuation in SPECT brain imaging

International Nuclear Information System (INIS)

Glick, S.J.; King, M.A.; Pan, T.S.; Soares, E.J.

1996-01-01

Accurate compensation for photon attenuation is needed to perform quantitative brain single-photon-emission computed tomographic (SPECT) imaging. Bellini's attenuation-compensation method has been used with a nonuniform attenuation map to account for the nonuniform attenuation properties of the head. Simulation studies using a three-dimensional (3-D) digitized anthropomorphic brain phantom were conducted to compare quantitative accuracy of reconstructions obtained with the nonuniform Bellini method to that obtained with the Chang method and to iterative reconstruction using maximum-likelihood expectation maximization (ML-EM). Using the Chang method and assuming the head to be a uniform attenuator gave reconstructions with an average bias of approximately 6-8%, whereas using the Bellini or the iterative ML-EM method with a nonuniform attenuation map gave an average bias of approximately 1%. The computation time required to implement nonuniform attenuation compensation with the Bellini algorithm is approximately equivalent to the time required to perform one iteration of ML-EM. Thus, using the Bellini method with a nonuniform attenuation map provides accurate compensation for photon attenuation within the head, and the method can be implemented in computation times suitable for routine clinical use

Application of the gamma-ray attenuation on the study of Amianthus-Cement tile with different ages

International Nuclear Information System (INIS)

Marques, Leonardo C.; Simeao, David da Silva; Oliveira, Ricardo Mendes de; Rocha, Wilson Roberto Dejato da; Costa, Elizabeth Cristina Soares da; Portezan Filho, Otavio; Coimbra, Melayne Martins

2005-01-01

In the civil construction, concrete of different resistances are prepared to assist to the objectives of the projects. Concrete samples, prepared in laboratory,can be used in the measurements of the density profiles along the sample, as well as to accompany the space and temporary evolution of the humidity in the process of water infiltration. Other material quite used in the civil construction it is the amianthus-cement tiles, that has good resistance to the deformation. This work intends to evaluate the homogeneity of the amianthus-cement tiles through the gamma-ray attenuation technique, in order to verify the possible existence of fissures or defects in the material, due to the aging and the bad weather. The first tile used was produced in 2002, te second one in 1991 and the third in 1978. Its dimensions were: 130x50x0,4 cm. To manipulate the tiles with easiness, these were divided in samples with the following dimensions: 12x8x0,4 cm. For each sample the linear attenuation coefficient was measured for a horizontal line, totalizing 14 points with an interval of 0,5 cm among the points. The measurement table used has a Na (Tl) scintillation detector of 2 x 2 , with circular collimator of 2 mm (for source) and of 5 mm (for the detector) and a radioactive source of 241 Am (59,6 keV, 100 mCi). With the measured values of the linear attenuation coefficient as a function of the position in the sample, we can build the curves of the linear attenuation coefficient versus position, which represent the homogeneity profile of the sample . The graphs of the linear attenuation coefficient versus position will be presented for the measured tiles as well as the statistical analysis of the results. (author)

The ultraviolet attenuation law in backlit spiral galaxies

International Nuclear Information System (INIS)

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

2014-01-01

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

The ultraviolet attenuation law in backlit spiral galaxies

Energy Technology Data Exchange (ETDEWEB)

Keel, William C. [Department of Physics and Astronomy, University of Alabama, Box 870324, Tuscaloosa, AL 35487 (United States); Manning, Anna M. [Stennis Space Center, MS 39522 (United States); Holwerda, Benne W. [ESA-ESTEC, Keplerlaan 1, 2201-AZ Noordwijk (Netherlands); Lintott, Chris J. [Astrophysics, Oxford University, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Schawinski, Kevin, E-mail: wkeel@ua.edu, E-mail: ammanning@bama.ua.edu, E-mail: bholwerd@rssd.esa.int, E-mail: Twitter@BenneHolwerda, E-mail: cjl@astro.ox.ac.uk, E-mail: Twitter@chrislintott, E-mail: kevin.schawinski@phys.ethz.ch, E-mail: Twitter@kevinschawinski [Institute for Astronomy, ETH Zürich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich (Switzerland)

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

Attenuation by a Human Body and Trees as well as Material Penetration Loss in 26 and 39 GHz Millimeter Wave Bands

Directory of Open Access Journals (Sweden)

Qi Wang

2017-01-01

Full Text Available This paper investigates the attenuation by a human body and trees as well as material penetration loss at 26 and 39 GHz by measurements and theoretical modeling work. The measurements were carried out at a large restaurant and a university campus by using a time domain channel sounder. Meanwhile, the knife-edge (KE model and one-cylinder and two-cylinder models based on uniform theory of diffraction (UTD are applied to model the shape of a human body and predict its attenuation in theory. The ITU (International Telecommunication Union and its modified models are used to predict the attenuation by trees. The results show that the upper bound of the KE model is better to predict the attenuation by a human body compared with UTD one-cylinder and two-cylinder models at both 26 and 39 GHz. ITU model overestimates the attenuation by willow trees, and a modified attenuation model by trees is proposed based on our measurements at 26 GHz. Penetration loss for materials such as wood and glass with different types and thicknesses is measured as well. The measurement and modeling results in this paper are significant and necessary for simulation and planning of fifth-generation (5G mm-wave radio systems in ITU recommended frequency bands at 26 and 39 GHz.

The effect of hydrate content on seismic attenuation: A case study for Mallik 2L-38 well data, Mackenzie delta, Canada

Science.gov (United States)

Chand, Shyam; Minshull, Tim A.

2004-07-01

Observations of velocities in sediments containing gas hydrates show that the strength of sediments increases with hydrate saturation. Hence it is expected that the attenuation of these sediments will decrease with increasing hydrate saturation. However, sonic log measurements in the Mallik 2L-38 well and cross hole tomography measurements in the Mallik field have shown that attenuation increases with hydrate saturation. We studied a range of mechanisms by which increasing hydrate saturation could cause increased attenuation. We found that a difference in permeability between the host sediment and the newly formed hydrate can produce the observed effect. We modelled attenuation in terms of Biot and squirt flow mechanisms in composite media. We have used our model to predict observed attenuations in the Mallik 2L-38 well, Mackenzie Delta, Canada.

Atmospheric Peroxy Radical Measurements by Chemical Amplification - Cavity Attenuated Phase Shift Spectroscopy

Science.gov (United States)

Wood, E. C.; Charest, J. R.

2013-12-01

We present a new chemical amplifier for the detection of peroxy radicals using Cavity Attenuated Phase Shift spectroscopy (CAPS) detection of NO2. The amplification scheme is similar to other chemical amplifiers and involves addition of CO (8%) and NO (3 ppm) to air sampled in a PFA tube. The chain length is quantified by amplification of a known concentration of methyl peroxy radicals (CH3O2) and peroxyacetyl radicals (CH3COO2) sampled by the instrument's reactor. The CH3O2 and CH3COO2 radicals are produced by photolysis of acetone at 254 nm and quantified by conversion to NO2 by reaction with excess NO. The chain length (CL) in dry air is over 200 and constant at RO2 concentrations under 500 ppt. The CL decreases by 55% at a relative humidity of 50%. A 0.95 cm (3/8') ID PFA tube, a 0.32 cm (1/8' ID) PFA tube, and a 0.48 cm ID quartz reactor give near-identical chain lengths and RH dependence, demonstrating the small importance of wall reactions (for clean tubing) as radical termination steps. The instrument comprises two independent inlets and CAPS detectors, allowing for simultaneous measurements in ROx mode (= NO2 + O3 + RO2 + HO2) and Ox mode (= NO2 + O3) thereby greatly reducing the effect of variations in background [Ox]. The 1σ precision of the instrument at constant background [Ox] and 0% relative humidity is 0.2 ppt ROx with 100 second averaging and increases to 0.3 ppt at an RH of 50%. The absolute uncertainty of the measurements is estimated as 20% and is affected by the accuracy of the NO2 calibration, the precision of the CAPS when calibrating at low RO2 concentrations, and the uncertainty in the photolysis quantum yield for the CH3CO + CH3 channel of acetone photolysis.

The diagnostic accuracy of pericolonic fat extension and attenuation for colorectal tumors

Energy Technology Data Exchange (ETDEWEB)

Zeina, Abdel-Rauf, E-mail: raufzeina3@hotmail.com [Department of Radiology, Hillel Yaffe Medical Center, Hadera (Israel); Affiliated with the Faculty of Medicine, Technion-Israel Institute of Technology, Haifa (Israel); Mahamid, Ahmad [Division of Surgery, Hillel Yaffe Medical Center, Hadera (Israel); Affiliated with the Faculty of Medicine, Technion-Israel Institute of Technology, Haifa (Israel); Walid, Saliba [Department of Internal Medicine C, Ha’emek Medical Center, Afula (Israel); Affiliated with the Faculty of Medicine, Technion-Israel Institute of Technology, Haifa (Israel); Nachtigal, Alicia; Shapira-Rootman, Mika [Department of Radiology, Hillel Yaffe Medical Center, Hadera (Israel); Affiliated with the Faculty of Medicine, Technion-Israel Institute of Technology, Haifa (Israel)

2015-09-15

Highlights: • Pericolonic fat extent and attenuation were higher in stage ≥T3 than attenuation, and maximal tumor diameter were assessed. • The application of all three parameters achieves 100% specificity. - Abstract: Objective: To evaluate the utility of quantitative analysis of the extension and attenuation of pericolonic fat in the local staging of colorectal cancer (CRC) using multi detector computed tomography (MDCT). Materials and methods: This was a retrospective study of 110 patients who were operated due to pathologically proven CRC from January 2007 to January 2010, and who underwent preoperative MDCT of the abdomen and pelvis with administration of intravenous contrast material and image acquisition during the portal venous phase. The mean age was 69 years (range of 38–90 years). Pathological reports were reviewed for TNM staging. All MDCT studies were reviewed by two certified radiologists for maximal and minimal tumor diameter, extent of the infiltrated pericolonic fat (measured in mm), attenuation of the infiltrated pericolonic fat (measured in Hounsfield units), and attenuation of normally appearing fat next to the tumor. The sensitivity and specificity of these parameters in detecting patients with ≥ T3 CRC were calculated. Results: The overall sensitivity, specificity, and accuracy of pericolonic fat infiltration in detecting patients with ≥T3 stage were 95% (95% CI, 89.0–98.7%), 20% (5.8–43.7%), and 81.9% (74.7–89%) respectively. The mean extent and attenuation of the infiltrated pericolonic fat, in addition to the maximal tumor diameter, were higher in the ≥T3 group (p < 0.05). By defining threshold values to these parameters, the positive predictive value for detecting ≥T3 stage tumors approaches 100%. Conclusion: Quantitative analysis of pericolonic fat

Enhanced replication of attenuated HSV-1 in irradiated human glioma xenografts

International Nuclear Information System (INIS)

Advani, Sunil J.; Kataoka, Yasushi; Sibley, Greg S.; Song, Paul Y.; Hallahan, Dennis E.; Roizman, Bernard; Weichselbaum, Ralph R.

1997-01-01

Purpose: Previously we had shown that combining ionizing radiation (IR) with attenuated replication competent HSV-1 (R3616) significantly increased glioma xenograft eradication compared to IR or virus alone. One hypothesis is that IR induces cell factors that contribute to augment viral replication thereby increasing the efficacy of attenuated HSV-1. The purpose of this study was to examine if IR altered viral replication of attenuated HSV-1 in glioma xenografts Material and Methods: Human U-87MG glioma cells were grown in the hindlimb of athymic mice and grown to >200 mm 3 . Tumors were infected with 2x10 7 plaque forming units (pfu) of R3616 ( γ1 34.5 - ) or R7020 (multimutated, γ1 34.5 + ) on day 0 and irradiated with 20 Gy on day 1 and 25 Gy on day 2. Tumors were harvested 3, 5, 7, and 14 days after viral injection. Tumors were homogenized and sonnicated. Serial dilutions of tumor extract were overlaid on Vero cells to determine the number of pfu. In addition, in-situ hybridization to HSV-1 DNA was performed on tumors harvested at day 7. Results: In-situ hybridization revealed larger numbers of glial cells infected with HSV along with a greater distribution in the irradiated tumors compared to non-irradiated tumors. We next quantified viral particles in infected tumors +/- IR: Conclusion: Herein we demonstrate radiation enhanced viral replication as one of the interactive effects of combining IR and attenuated HSV in treating glioma xenografts and a potential therapeutic motif in the treatment of gliomas. To reduce normal tissue toxicity of HSV in glioma therapy, viruses must be attenuated. However, attenuating the virus compromises its replication and thus its potential efficacy. Our results indicate that IR augments the amount of virus recovered from human glioma xenografts for up to 3 days post IR. The results do not appear to be related to a specific mutation in the herpes genome but rather to herpes viruses in general. Yields of R7020 were greater than R

Effect of X-Ray Attenuation of Arterial Obstructions on Intravenous Thrombolysis and Outcome after Ischemic Stroke.

Directory of Open Access Journals (Sweden)

Grant Mair

Full Text Available To assess whether the x-ray attenuation of intra-arterial obstruction measured on non-contrast CT in ischemic stroke can predict response to thrombolysis and subsequent functional outcome.The Third International Stroke Trial (IST-3 was a multicenter randomized-controlled trial of intravenous thrombolysis (rt-PA given within six hours of ischemic stroke. Ethical approval and informed consent were obtained. In a subgroup of 109 IST-3 patients (38 men, median age 82 years, a single reader, masked to all clinical and other imaging data, manually measured x-ray attenuation (Hounsfield Units, HU on non-contrast CT at the location of angiographically-proven intra-arterial obstructions, pre-randomization and at 24-48 hour follow-up. We calculated change in attenuation between scans. We assessed the impact of pre-randomization arterial obstruction attenuation on six-month functional outcome.Most arterial obstructions (64/109, 59% were hyperattenuating (mean 51.0 HU. Compared with control, treatment with rt-PA was associated with a greater, but non-significant, reduction in obstruction attenuation at follow-up (-8.0 HU versus -1.4 HU in patients allocated control, p = 0.117. In multivariable ordinal regression analysis controlled for patient age, stroke severity, location and extent of obstruction, time from stroke onset to baseline scan and rt-PA treatment allocation, the attenuation of pre-randomization arterial obstruction was not independently associated with six-month outcome (odds ratio = 0.99, 95% confidence interval = 0.94-1.03, p = 0.516.In ischemic stroke, the x-ray attenuation of the arterial obstruction may decline more rapidly from baseline to 24-48 hours following treatment with thrombolysis but we found no evidence that baseline arterial obstruction attenuation predicts six-month outcome.

P300 is attenuated during dissociative episodes.

Science.gov (United States)

Kirino, Eiji

2006-02-01

The present study examined the pathophysiology of dissociative phenomena using the P300 component of event-related potentials, quantitative electroencephalography (QEEG), and morphology measures of computed tomography scan. Event-related potentials during an auditory oddball paradigm and QEEG in resting state were recorded. Patients exhibited attenuation of P300 amplitudes compared with controls during dissociative episodes, but exhibited recovery to control levels in remission. Patients had a larger Sylvian fissure-brain ratio than did controls. QEEG findings revealed no significant differences between the patients and controls or between episodes and remission in the patient group. Attenuation of the P300 can be interpreted as the result of a negative feedback loop from the medial temporal lobe to the cortex, which decreases the amount of information flow, allocation of attentional resources, and updating of working memory to avoid both excessive long-term memory system activity in medial temporal lobe and resurgence of affect-laden memories.

Ultrasonic attenuation as a function of heat treatment and grain size in 79Ni--6Mo--15Fe alloy

International Nuclear Information System (INIS)

Gieske, J.H.

1978-03-01

A pulse echo ultrasonic technique was used to measure the attenuation coefficient for 79Ni-6Mo-15Fe alloy specimens. The attenuation coefficient was determined using a 25 MHz ultrasonic transducer for specimens which had undergone different time-temperature heat treatments. The ultrasonic attenuation data versus heat treat time was used to assess grain size growth in the specimens

An acoustic eikonal equation for attenuating VTI media

KAUST Repository

Hao, Qi

2016-09-06

We present an acoustic eikonal equation governing the complex-valued travel time of P-waves in attenuating, transversely isotropic media with a vertical symmetry axis (VTI). This equation is based on the assumption that the Pwave complex-valued travel time is independent of the Swave velocity parameter v in Thomsen\\'s notation and the attenuation coefficient A in the Thomsen-type notation for attenuating VTI media. We combine perturbation theory and Shanks transform to develop practical approximations to the attenuating acoustic eikonal equation, capable of admitting analytical description of the attenuation in homogeneous media. For a horizontal, attenuating VTI layer, we also derive non-hyperbolic approximations for the real and imaginary parts of the complex-valued reflection travel time.

Characteristics of liver tissue for attenuate the gamma radiation; Caracteristicas del tejido hepatico para atenuar la radiacion gamma

Energy Technology Data Exchange (ETDEWEB)

Arcos P, A.; Rodriguez N, S.; Pinedo S, A.; Amador V, P.; Chacon R, A.; Vega C, H.R. [Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)

2005-07-01

It was determined the lineal attenuation coefficient of hepatic tissue before gamma radiation of a source of {sup 137} Cs. When exposing organic material before X or gamma radiation fields, part of the energy of the photons is absorbed by the material, while another part crosses it without producing any effect. The quantity of energy that is absorbed is a measure of the dose that receives the material. The three main mechanisms by means of which the gamma rays interacting with the matter are: The Photoelectric Effect, the Compton dispersion and the Even production; the sum of these three processes is translated in the attenuation coefficient of the radiation. In this work we have used hepatic tissue of bovine, as substitute of the human hepatic tissue, and we have measured the lineal attenuation coefficient for photons of 0.662 MeV. Through a series of calculations we have determined the lineal attenuation coefficient for photons from 10{sup -3} to 10{sup -5} MeV and the measured coefficient was compared with the one calculated. (Author)

Ultrasonic attenuation in superconducting zinc

International Nuclear Information System (INIS)

Auluck, S.

1978-01-01

The differences in the Zn ultrasonic attenuation data of different workers are analyzed. The superconducting energy gaps deduced from our analysis of the ultrasonic-attenuation data of Cleavelin and Marshall are consistent with the gaps deduced from the knowledge of the Fermi surface and the electron-phonon mass enhancement factor

[Prevalence of previously diagnosed diabetes mellitus in Mexico.

Science.gov (United States)

Rojas-Martínez, Rosalba; Basto-Abreu, Ana; Aguilar-Salinas, Carlos A; Zárate-Rojas, Emiliano; Villalpando, Salvador; Barrientos-Gutiérrez, Tonatiuh

2018-01-01

To compare the prevalence of previously diagnosed diabetes in 2016 with previous national surveys and to describe treatment and its complications. Mexico's national surveys Ensa 2000, Ensanut 2006, 2012 and 2016 were used. For 2016, logistic regression models and measures of central tendency and dispersion were obtained. The prevalence of previously diagnosed diabetes in 2016 was 9.4%. The increase of 2.2% relative to 2012 was not significant and only observed in patients older than 60 years. While preventive measures have increased, the access to medical treatment and lifestyle has not changed. The treatment has been modified, with an increase in insulin and decrease in hypoglycaemic agents. Population aging, lack of screening actions and the increase in diabetes complications will lead to an increase on the burden of disease. Policy measures targeting primary and secondary prevention of diabetes are crucial.

Influence of fluid-attenuated inversion-recovery on stroke apparent diffusion coefficient measurements and its clinical application

Energy Technology Data Exchange (ETDEWEB)

Ni Jianming [Medical Imaging Department, Wuxi Second Hospital Affiliated Nanjing Medical University, 68 Zhong Shan Road, Wuxi, Jiangsu Province 214002 (China); Radiology Department, Huashan Hospital, Shanghai Medical College, Fudan University, 12 Urumqi Middle Road, Shanghai 200040 (China); Nuclear Medicine Department, Renji Hospital, Medical School of Jiaotong University, Dongfang Road 1630, Shanghai 200127 (China); Mogensen, Monique A. [Department of Radiology, Division of Neuroradiology, University of Southern California, Los Angeles, CA (United States); Chen Zengai [Radiology Department, Huashan Hospital, Shanghai Medical College, Fudan University, 12 Urumqi Middle Road, Shanghai 200040 (China); Nuclear Medicine Department, Renji Hospital, Medical School of Jiaotong University, Dongfang Road 1630, Shanghai 200127 (China); Shuang Chen; Shen Tianzhen [Radiology Department, Huashan Hospital, Shanghai Medical College, Fudan University, 12 Urumqi Middle Road, Shanghai 200040 (China); Huang Gang, E-mail: huang2802@163.co [Nuclear Medicine Department, Renji Hospital, Medical School of Jiaotong University, Dongfang Road 1630, Shanghai 200127 (China)

2010-08-15

Background and purpose: The application of a fluid-attenuated inversion-recovery pulse with a conventional diffusion-weighted MRI sequence (FLAIR DWI) decreases the partial volume effects from cerebrospinal fluid on apparent diffusion coefficient (ADC) measurements. For this reason, FLAIR DWI may be more useful in the evaluation of ischemic stroke, but few studies have looked at the effect of FLAIR on ADC measurements in this setting. This study quantitatively compares FLAIR DWI and conventional DWI in ischemic stroke of varying ages to assess the potential advantages of this technique. Methods: We respectively analyzed 139 DWI studies in patients with ischemic stroke with and without FLAIR at varying time points ranging from hyperacute to chronic. ADC values were measured in each lesion, as well as in the contralateral normal side. Comparisons were made between the ADC values obtained from the DWI sequences with and without FLAIR for both the lesion and the normal contralateral side. Results: The ADC measurements within the ischemic lesion were very similar on FLAIR DWI and conventional DWI for lesions less than 14 days old (p > 0.05), but were significantly decreased on FLAIR DWI for lesions between 15 and 30 days old and in lesions >31 days old (chronic stage) (p < 0.01). The contralateral ADC values were all significantly decreased on the FLAIR DWI sequence compared with conventional DWI (p < 0.01). Conclusions: The application of an inversion pulse does not significantly affect the ADC values for early stage ischemic stroke (less than 14 days from symptom onset), but results in a more accurate relative ADC measurement by reducing the cerebrospinal fluid partial volume effects of the normal contralateral side. In addition, combined with the conventional DWI, FLAIR DWI may be helpful in determining the age of ischemic lesions.

Integrated PET/MR breast cancer imaging: Attenuation correction and implementation of a 16-channel RF coil

Energy Technology Data Exchange (ETDEWEB)

Oehmigen, Mark, E-mail: mark.oehmigen@uni-due.de; Lindemann, Maike E. [High Field and Hybrid MR Imaging, University Hospital Essen, Essen 45147 (Germany); Lanz, Titus [Rapid Biomedical GmbH, Rimpar 97222 (Germany); Kinner, Sonja [Institute for Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen 45147 (Germany); Quick, Harald H. [High Field and Hybrid MR Imaging, University Hospital Essen, Essen 45147, Germany and Erwin L. Hahn Institute for MR Imaging, University Duisburg-Essen, Essen 45141 (Germany)

2016-08-15

Purpose: This study aims to develop, implement, and evaluate a 16-channel radiofrequency (RF) coil for integrated positron emission tomography/magnetic resonance (PET/MR) imaging of breast cancer. The RF coil is designed for optimized MR imaging performance and PET transparency and attenuation correction (AC) is applied for accurate PET quantification. Methods: A 16-channel breast array RF coil was designed for integrated PET/MR hybrid imaging of breast cancer lesions. The RF coil features a lightweight rigid design and is positioned with a spacer at a defined position on the patient table of an integrated PET/MR system. Attenuation correction is performed by generating and applying a dedicated 3D CT-based template attenuation map. Reposition accuracy of the RF coil on the system patient table while using the positioning frame was tested in repeated measurements using MR-visible markers. The MR, PET, and PET/MR imaging performances were systematically evaluated using modular breast phantoms. Attenuation correction of the RF coil was evaluated with difference measurements of the active breast phantoms filled with radiotracer in the PET detector with and without the RF coil in place, serving as a standard of reference measurement. The overall PET/MR imaging performance and PET quantification accuracy of the new 16-channel RF coil and its AC were then evaluated in first clinical examinations on ten patients with local breast cancer. Results: The RF breast array coil provides excellent signal-to-noise ratio and signal homogeneity across the volume of the breast phantoms in MR imaging and visualizes small structures in the phantoms down to 0.4 mm in plane. Difference measurements with PET revealed a global loss and thus attenuation of counts by 13% (mean value across the whole phantom volume) when the RF coil is placed in the PET detector. Local attenuation ranging from 0% in the middle of the phantoms up to 24% was detected in the peripheral regions of the phantoms at

L-ascorbate attenuates methamphetamine neurotoxicity through enhancing the induction of endogenous heme oxygenase-1.

Science.gov (United States)

Huang, Ya-Ni; Wang, Jiz-Yuh; Lee, Ching-Tien; Lin, Chih-Hung; Lai, Chien-Cheng; Wang, Jia-Yi

2012-12-01

Methamphetamine (METH) is a drug of abuse which causes neurotoxicity and increased risk of developing neurodegenerative diseases. We previously found that METH induces heme oxygenase (HO)-1 expression in neurons and glial cells, and this offers partial protection against METH toxicity. In this study, we investigated the effects of l-ascorbate (vitamin C, Vit. C) on METH toxicity and HO-1 expression in neuronal/glial cocultures. Cell viability and damage were evaluated by 3-(4,5-dimethylthianol-2-yl)-2,5 diphenyl tetrazolium bromide (MTT) reduction and lactate dehydrogenase (LDH) release, respectively. Neuronal and glial localization of HO-1 were identified by double immunofluorescence staining. Reactive oxygen species (ROS) production was measured using the fluorochrome 2',7'-dichlorofluorescin diacetate. HO-1 mRNA and protein expression were examined by RT-qPCR and Western blotting, respectively. Results show that Vit. C induced HO-1 mRNA and protein expressions in time- and concentration-dependent manners. Inhibition of p38 mitogen-activated protein kinase (MAPK) but not extracellular signal-regulated kinase (ERK) significantly blocked induction of HO-1 by Vit. C. HO-1 mRNA and protein expressions were significantly elevated by a combination of Vit. C and METH, compared to either Vit. C or METH alone. Pretreatment with Vit. C enhanced METH-induced HO-1 expression and attenuated METH-induced ROS production and neurotoxicity. Pharmacological inhibition of HO activity abolished suppressive effects of Vit. C on METH-induced ROS production and attenuated neurotoxicity. We conclude that induction of HO-1 expression contributes to the attenuation of METH-induced ROS production and neurotoxicity by Vit. C. We suggest that HO-1 induction by Vit. C may serve as a strategy to alleviate METH neurotoxicity. Copyright © 2012 Elsevier Inc. All rights reserved.

Attenuation of the gamma rays in tissues; Atenuacion de los rayos gamma en tejidos

Energy Technology Data Exchange (ETDEWEB)

Arcos P, A.; Rodriguez N, S.; Pinedo S, A.; Amador V, P.; Chacon R, A.; Vega C, H.R. [Unidad Academica de Estudios Nucleares, Cipres 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)

2005-07-01

The mass and lineal attenuation coefficient and of hepatic tissue, muscular, osseous and of brain before gamma rays of 10{sup -3} to 10{sup 5} MeV were calculated. For the case of the osseous tissue the calculation was made for the cartilage, the cortical tissue and the bone marrow. During the calculations the elementary composition of the tissues of human origin was used. The calculations include by separate the Photoelectric effect, the Compton scattering and the Pair production, as well as the total. For to establish a comparison with the attenuation capacities, the coefficients of the water, the aluminum and the lead also were calculated. The study was complemented measuring the attenuation coefficient of hepatic tissue of bovine before gamma rays of 0.662 MeV of a source of {sup 137} Cs. The measurement was made through of an experiment of photons transmission through samples frozen of hepatic tissue and with a Geiger-Mueller detector. (Author)

Cyclooxygenase inhibitors attenuate bradykinin-induced vasoconstriction in septic isolated rat lungs

NARCIS (Netherlands)

Fischer, L. G.; Hollmann, M. W.; Horstman, D. J.; Rich, G. F.

2000-01-01

Cyclooxygenase (COX) products play an important role in modulating sepsis and subsequent endothelial injury. We hypothesized that COX inhibitors may attenuate endothelial dysfunction during sepsis, as measured by receptor-mediated bradykinin (BK)-induced vasoconstriction and/or receptor-independent

Characterization and Monitoring of Natural Attenuation of Chlorinated Solvents in Ground Water: A Systems Approach

Science.gov (United States)

Cutshall, N. H.; Gilmore, T.; Looney, B. B.; Vangelas, K. M.; Adams, K. M.; Sink, C. H.

2006-05-01

Like many US industries and businesses, the Department of Energy (DOE) is responsible for remediation and restoration of soils and ground water contaminated with chlorinated ethenes. Monitored Natural Attenuation (MNA) is an attractive remediation approach and is probably the universal end-stage technology for removing such contamination. Since 2003 we have carried out a multifaceted program at the Savannah River Site designed to advance the state of the art for MNA of chlorinated ethenes in soils and groundwater. Three lines of effort were originally planned: 1) Improving the fundamental science for MNA, 2) Promoting better characterization and monitoring (CM) techniques, and 3) Advancing the regulatory aspects of MNA management. A fourth line, developing enhanced attenuation methods based on sustainable natural processes, was added in order to deal with sites where the initial natural attenuation capacity cannot offset contaminant loading rates. These four lines have been pursued in an integrated and mutually supportive fashion. Many DOE site-cleanup program managers view CM as major expenses, especially for natural attenuation where measuring attenuation is complex and the most critical attenuation mechanisms cannot be determined directly. We have reviewed new and developing approaches to CM for potential application in support of natural attenuation of chlorinated hydrocarbons in ground water at DOE sites (Gilmore, Tyler, et al., 2006 WSRC-TR- 2005-00199). Although our project is focused on chlorinated ethenes, many of the concepts and strategies are also applicable to a wider range of contaminants including radionuclides and metals. The greatest savings in CM are likely to come from new management approaches. New approaches can be based, for example, on conceptual models of attenuation capacity, the ability of a formation to reduce risks caused by contaminants. Using the mass balance concept as a guide, the integrated mass flux of contaminant is compared to

Radiation protection clothing in X-ray diagnostics. Comparison of attenuation equivalents in narrow beam and inverse broad-beam geometry

International Nuclear Information System (INIS)

Pichler, Thomas; Schoepf, T.; Ennemoser, O.

2011-01-01

Purpose: Standard DIN EN 61 331-1 for attenuation measurements in the narrow and broad beam as well as DIN 6857-1 for the determination of shielding properties in the inverse broad-beam geometry are available for testing the attenuation of protection clothing. The attenuation measurements in the narrow beam don't consider scattered radiation and fluorescence due to the arrangement. This leads to the fact that the protective effect of lead-free materials will be misestimated when compared to lead. Therefore, the differences in attenuation equivalents, determined by both test methods for topical radiation protection aprons, were examined. Materials and Methods: The attenuations in inverse broad-beam geometry according to DIN 6857-1 and in the narrow beam according to DIN EN 61 331-1 were measured using commercially available aprons. They were made of lead, lead-reduced and lead-free materials. For determination of the attenuation equivalents, certificated lead-foils with high purity and a precise thickness of 0.1 to 1.25 mm were used. Results: The measurements in the narrow beam according to DIN EN 61 331-1 showed that nearly all aprons reach the required lead equivalent at mid-range tube voltages of 100 kV. At higher and lower tube voltages, the requirements of DIN EN 61 331-3 were largely not met. In contrast, the testing of the same aprons in inverse broad-beam geometry according to DIN 6857-1 showed that only a few aprons meet the requirements for being classified in the nominal protection class. Conclusion: The measurements suggest that testing method DIN 6857-1 has yet to prevail and that manufacturers are just beginning to develop the appropriate protective materials. (orig.)

Context-dependent efficacy of a counter-conditioning strategy with atypical neuroleptic drugs in mice previously sensitized to cocaine.

Science.gov (United States)

Oliveira-Lima, A J; Marinho, Eav; Santos-Baldaia, R; Hollais, A W; Baldaia, M A; Talhati, F; Ribeiro, L T; Wuo-Silva, R; Berro, L F; Frussa-Filho, R

2017-02-06

We have previously demonstrated that treatment with ziprasidone and aripiprazole selectively inhibit the development of behavioral sensitization to cocaine in mice. We now investigate their effects on a counter-conditioning strategy in mice and the importance of the treatment environment for this phenomenon. Evaluate the context-specificity of ziprasidone and aripiprazole on conditioned locomotion to cocaine and cocaine-induced hyperlocomotion and behavioral sensitization in a counter-conditioning strategy in mice. Animals were sensitized with saline or cocaine injections in the open-field apparatus in a 15-day intermittent treatment and subsequently treated with vehicle, 5mg/kg ziprasidone or 0.1mg/kg aripiprazole paired to the open-field or the home-cage for 4 alternate days. Mice were then challenged with saline and cocaine in the open-field apparatus on subsequent days. While treatment with ziprasidone decreased spontaneous locomotion and conditioned locomotion alike, treatment with aripiprazole specifically attenuated the expression of conditioned hyperlocomotion to cocaine. Ziprasidone and aripiprazole had no effects on cocaine-induced conditioned hyperlocomotion observed during saline challenge after drug withdrawal. Treatment with either ziprasidone or aripiprazole when previously given in the cocaine-paired environment attenuated the subsequent expression of behavioral sensitization to cocaine. Animals treated with aripiprazole in the open-field, but not in the home-cage, showed a blunted response to cocaine when receiving a cocaine challenge for the first time. Both neuroleptic drugs showed a context-dependent effectiveness in attenuating long-term expression of cocaine-induced behavioral sensitization when administered in the cocaine-associated environment, with aripiprazole also showing effectiveness in blocking the expression of acute cocaine effects. Copyright © 2016. Published by Elsevier Inc.

ENHANCEMENTS TO NATURAL ATTENUATION: SELECTED CASE STUDIES

Energy Technology Data Exchange (ETDEWEB)

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).

Evaluation of the attenuation properties of MR equipment for its use in a whole-body PET/MR scanner

International Nuclear Information System (INIS)

Delso, G; Martinez-Moeller, A; Bundschuh, R A; Ziegler, S I; Ladebeck, R; Candidus, Y; Faul, D

2010-01-01

The combination of magnetic resonance imaging (MR) and positron emission tomography (PET) scanners can provide a powerful tool for clinical diagnosis and investigation. Among the challenges of developing a combined scanner, obtaining attenuation maps for PET reconstruction is of critical importance. This requires accounting for the presence of MR hardware in the field of view. The attenuation introduced by this hardware cannot be obtained from MR data. We propose the creation of attenuation models of MR hardware, to be registered into the MR-based attenuation map prior to PET reconstruction. Two steps were followed to assess the viability of this method. First, transmission and emission measurements were performed on MR components (RF coils and medical probes). The severity of the artifacts in the reconstructed PET images was evaluated. Secondly, a high-exposure computed tomography (CT) scan was used to obtain a model of a head coil. This model was registered into the attenuation map of PET/CT scans of a uniform phantom fitted with the coil. The resulting PET images were compared to the PET/CT reconstruction in the absence of coils. The artifacts introduced by misregistration of the model were studied. The transmission scans revealed 17% count loss due to the presence of head and neck coils in the field of view. Important sources of attenuation were found in the lock, signal cables and connectors. However, the worst source of attenuation was the casing between both coils. None of the measured medical probes introduced a significant amount of attenuation. Concerning the attenuation model of the head coil, reconstructed PET images with model-based correction were comparable to the reference PET/CT reconstruction. However, inaccuracies greater than 1-2 mm in the axial positioning of the model led to important artifacts. In conclusion, the results show that model-based attenuation correction is possible. Using a high-exposure scan to create an attenuation model of the

Clinical evaluation of respiration-induced attenuation uncertainties in pulmonary 3D PET/CT.

Science.gov (United States)

Kruis, Matthijs F; van de Kamer, Jeroen B; Vogel, Wouter V; Belderbos, José Sa; Sonke, Jan-Jakob; van Herk, Marcel

2015-12-01

In contemporary positron emission tomography (PET)/computed tomography (CT) scanners, PET attenuation correction is performed by means of a CT-based attenuation map. Respiratory motion can however induce offsets between the PET and CT data. Studies have demonstrated that these offsets can cause errors in quantitative PET measures. The purpose of this study is to quantify the effects of respiration-induced CT differences on the attenuation correction of pulmonary 18-fluordeoxyglucose (FDG) 3D PET/CT in a patient population and to investigate contributing factors. For 32 lung cancer patients, 3D-CT, 4D-PET and 4D-CT data were acquired. The 4D FDG PET data were attenuation corrected (AC) using a free-breathing 3D-CT (3D-AC), the end-inspiration CT (EI-AC), the end-expiration CT (EE-AC) or phase-by-phase (P-AC). After reconstruction and AC, the 4D-PET data were averaged. In the 4Davg data, we measured maximum tumour standardised uptake value (SUV)max in the tumour, SUVmean in a lung volume of interest (VOI) and average SUV (SUVmean) in a muscle VOI. On the 4D-CT, we measured the lung volume differences and CT number changes between inhale and exhale in the lung VOI. Compared to P-AC, we found -2.3% (range -9.7% to 1.2%) lower tumour SUVmax in EI-AC and 2.0% (range -0.9% to 9.5%) higher SUVmax in EE-AC. No differences in the muscle SUV were found. The use of 3D-AC led to respiration-induced SUVmax differences up to 20% compared to the use of P-AC. SUVmean differences in the lung VOI between EI-AC and EE-AC correlated to average CT differences in this region (ρ = 0.83). SUVmax differences in the tumour correlated to the volume changes of the lungs (ρ = -0.55) and the motion amplitude of the tumour (ρ = 0.53), both as measured on the 4D-CT. Respiration-induced CT variations in clinical data can in extreme cases lead to SUV effects larger than 10% on PET attenuation correction. These differences were case specific and correlated to differences in CT number

A study on dose attenuation in bone density when TBI using diode detector and TLD

International Nuclear Information System (INIS)

Im, Hyun Sil; Lee, Jung Jin; Jang, Ahn Ki; KIm, Wan Sun

2003-01-01

Uniform dose distribution of the whole body is essential factor for the total body irradiation(TBI). In order to achieved this goal, we used to compensation filter to compensate body contour irregularity and thickness differences. But we can not compensate components of body, namely lung or bone. The purpose of this study is evaluation of dose attenuation in bone tissue when TBI using diode detectors and TLD system. The object of this study were 5 patients who undergo TBI at our hospital. Dosimetry system were diode detectors and TLD system. Treatment method was bilateral and delivered 10 MV X-ray from linear accelerator. Measurement points were head, neck, pelvis, knees and ankles. TLD used two patients and diode detectors used three patients. Results are as followed. All measured dose value were normalized skin dose. TLD dosimetry : Measured skin dose of head, neck, pelvis, knees and ankles were 92.78±3.3, 104.34±2.3, 98.03±1.4, 99.9±2.53, 98.17±0.56 respectably. Measured mid-depth dose of pelvis, knees and ankles were 86±1.82, 93.24±2.53, 91.50±2.84 respectably. There were 6.67%-11.65% dose attenuation at mid-depth in pelvis, knees and ankles. Diode detector : Measured skin dose of head, neck, pelvis, knees and ankles were 95.23±1.18, 98.33±0.6, 93.5±1.5, 87.3±1.5, 86.90±1.16 respectably. There were 4.53%-12.6% dose attenuation at mid-depth in pelvis, knees and ankles. We concluded that dose measurement with TLD or diode detector was inevitable when TBI treatment. Considered dose attenuation in bone tissue, We must have adequately deduction of compensator thickness that body portion involved bone tissue.

Light attenuation in estuarine mangrove lakes

Science.gov (United States)

Frankovich, Thomas A.; Rudnick, David T.; Fourqurean, James W.

2017-01-01

Submerged aquatic vegetation (SAV) cover has declined in brackish lakes in the southern Everglades characterized by low water transparencies, emphasizing the need to evaluate the suitability of the aquatic medium for SAV growth and to identify the light attenuating components that contribute most to light attenuation. Underwater attenuation of downwards irradiance of photosynthetically active radiation (PAR) was determined over a three year period at 42 sites in shallow (freshwater flow into these areas may dilute CDOM concentrations and improve the salinity and light climate for SAV communities.

Outdoor FSO Communications Under Fog: Attenuation Modeling and Performance Evaluation

KAUST Repository

Esmail, Maged Abdullah

2016-07-18

Fog is considered to be a primary challenge for free space optics (FSO) systems. It may cause attenuation that is up to hundreds of decibels per kilometer. Hence, accurate modeling of fog attenuation will help telecommunication operators to engineer and appropriately manage their networks. In this paper, we examine fog measurement data coming from several locations in Europe and the United States and derive a unified channel attenuation model. Compared with existing attenuation models, our proposed model achieves a minimum of 9 dB, which is lower than the average root-mean-square error (RMSE). Moreover, we have investigated the statistical behavior of the channel and developed a probabilistic model under stochastic fog conditions. Furthermore, we studied the performance of the FSO system addressing various performance metrics, including signal-to-noise ratio (SNR), bit-error rate (BER), and channel capacity. Our results show that in communication environments with frequent fog, FSO is typically a short-range data transmission technology. Therefore, FSO will have its preferred market segment in future wireless fifth-generation/sixth-generation (5G/6G) networks having cell sizes that are lower than a 1-km diameter. Moreover, the results of our modeling and analysis can be applied in determining the switching/thresholding conditions in highly reliable hybrid FSO/radio-frequency (RF) networks.

Reconstruction of bremsstrahlung spectra from attenuation data using generalized simulated annealing

International Nuclear Information System (INIS)

Menin, O.H.; Martinez, A.S.; Costa, A.M.

2016-01-01

A generalized simulated annealing algorithm, combined with a suitable smoothing regularization function is used to solve the inverse problem of X-ray spectrum reconstruction from attenuation data. The approach is to set the initial acceptance and visitation temperatures and to standardize the terms of objective function to automate the algorithm to accommodate different spectra ranges. Experiments with both numerical and measured attenuation data are presented. Results show that the algorithm reconstructs spectra shapes accurately. It should be noted that in this algorithm, the regularization function was formulated to guarantee a smooth spectrum, thus, the presented technique does not apply to X-ray spectrum where characteristic radiation are present. - Highlights: • X-ray spectra reconstruction from attenuation data using generalized simulated annealing. • Algorithm employs a smoothing regularization function, and sets the initial acceptance and visitation temperatures. • Algorithmic is automated by standardizing the terms of the objective function. • Algorithm is compared with classical methods.

Estimation of diffuse attenuation of ultraviolet light in optically shallow Florida Keys waters from MODIS measurements

Science.gov (United States)

Diffuse attenuation of solar light (Kd, m−1) determines the percentage of light penetrating the water column and available for benthic organisms. Therefore, Kd can be used as an index of water quality for coastal ecosystems that are dependent on photosynthesis, such as the coral ...

NEBULAR ATTENUATION IN Hα-SELECTED STAR-FORMING GALAXIES AT z = 0.8 FROM THE NewHα SURVEY

International Nuclear Information System (INIS)

Momcheva, Ivelina G.; Lee, Janice C.; Ouchi, Masami; Ly, Chun; Salim, Samir; Dale, Daniel A.; Finn, Rose; Ono, Yoshiaki

2013-01-01

We present measurements of the dust attenuation of Hα-selected emission-line galaxies at z = 0.8 from the NewHα narrowband survey. The analysis is based on deep follow-up spectroscopy with Magellan/IMACS, which captures the strong rest-frame optical emission lines from [O II] λ3727 to [O III] λ5007. The spectroscopic sample used in this analysis consists of 341 confirmed Hα emitters. We place constraints on the active galactic nucleus (AGN) fraction using diagnostics that can be applied at intermediate redshift. We find that at least 5% of the objects in our spectroscopic sample can be classified as AGNs and 2% are composite, i.e., powered by a combination of star formation and AGN activity. We measure the dust attenuation for individual objects from the ratios of the higher order Balmer lines. The Hβ and Hγ pair of lines is detected with S/N > 5 in 55 individual objects and the Hβ and Hδ pair is detected in 50 individual objects. We also create stacked spectra to probe the attenuation in objects without individual detections. The median attenuation at Hα based on the objects with individually detected lines is A(Hα) = 0.9 ± 1.0 mag, in good agreement with the attenuation found in local samples of star-forming galaxies. We find that the z = 0.8 galaxies occupy a similar locus of attenuation as a function of magnitude, mass, and star formation rate (SFR) as a comparison sample drawn from the SDSS DR4. Both the results from the individual z = 0.8 galaxies and from the stacked spectra show consistency with the mass-attenuation and SFR-attenuation relations found in the local universe, indicating that these relations are also applicable at intermediate redshift.

Believing and perceiving: authorship belief modulates sensory attenuation.

Directory of Open Access Journals (Sweden)

Andrea Desantis

Full Text Available Sensory attenuation refers to the observation that self-generated stimuli are attenuated, both in terms of their phenomenology and their cortical response compared to the same stimuli when generated externally. Accordingly, it has been assumed that sensory attenuation might help individuals to determine whether a sensory event was caused by themselves or not. In the present study, we investigated whether this dependency is reciprocal, namely whether sensory attenuation is modulated by prior beliefs of authorship. Participants had to judge the loudness of auditory effects that they believed were either self-generated or triggered by another person. However, in reality, the sounds were always triggered by the participants' actions. Participants perceived the tones' loudness attenuated when they believed that the sounds were self-generated compared to when they believed that they were generated by another person. Sensory attenuation is considered to contribute to the emergence of people's belief of authorship. Our results suggest that sensory attenuation is also a consequence of prior belief about the causal link between an action and a sensory change in the environment.

X-ray-based attenuation correction for positron emission tomography/computed tomography scanners.

Science.gov (United States)

Kinahan, Paul E; Hasegawa, Bruce H; Beyer, Thomas

2003-07-01

A synergy of positron emission tomography (PET)/computed tomography (CT) scanners is the use of the CT data for x-ray-based attenuation correction of the PET emission data. Current methods of measuring transmission use positron sources, gamma-ray sources, or x-ray sources. Each of the types of transmission scans involves different trade-offs of noise versus bias, with positron transmission scans having the highest noise but lowest bias, whereas x-ray scans have negligible noise but the potential for increased quantitative errors. The use of x-ray-based attenuation correction, however, has other advantages, including a lack of bias introduced from post-injection transmission scanning, which is an important practical consideration for clinical scanners, as well as reduced scan times. The sensitivity of x-ray-based attenuation correction to artifacts and quantitative errors depends on the method of translating the CT image from the effective x-ray energy of approximately 70 keV to attenuation coefficients at the PET energy of 511 keV. These translation methods are usually based on segmentation and/or scaling techniques. Errors in the PET emission image arise from positional mismatches caused by patient motion or respiration differences between the PET and CT scans; incorrect calculation of attenuation coefficients for CT contrast agents or metallic implants; or keeping the patient's arms in the field of view, which leads to truncation and/or beam-hardening (or x-ray scatter) artifacts. Proper interpretation of PET emission images corrected for attenuation by using the CT image relies on an understanding of the potential artifacts. In cases where an artifact or bias is suspected, careful inspection of all three available images (CT and PET emission with and without attenuation correction) is recommended. Copyright 2003 Elsevier Inc. All rights reserved.

Lidocaine attenuates anisomycin-induced amnesia and release of norepinephrine in the amygdala

Science.gov (United States)

Sadowski, Renee N.; Canal, Clint E.; Gold, Paul E.

2011-01-01

When administered near the time of training, protein synthesis inhibitors such as anisomycin impair later memory. A common interpretation of these findings is that memory consolidation requires new protein synthesis initiated by training. However, recent findings support an alternative interpretation that abnormally large increases in neurotransmitter release after injections of anisomycin may be responsible for producing amnesia. In the present study, a local anesthetic was administered prior to anisomycin injections in an attempt to mitigate neurotransmitter actions and thereby attenuate the resulting amnesia. Rats received lidocaine and anisomycin injections into the amygdala 130 and 120 min, respectively, prior to inhibitory avoidance training. Memory tests 48 hr later revealed that lidocaine attenuated anisomycin-induced amnesia. In other rats, in vivo microdialysis was performed at the site of amygdala infusion of lidocaine and anisomycin. As seen previously, anisomycin injections produced large increases in release of norepinephrine in the amygdala. Lidocaine attenuated the anisomycin-induced increase in release of norepinephrine but did not reverse anisomycin inhibition of protein synthesis, as assessed by c-Fos immunohistochemistry. These findings are consistent with past evidence suggesting that anisomycin causes amnesia by initiating abnormal release of neurotransmitters in response to the inhibition of protein synthesis. PMID:21453778

Underwater image enhancement based on the dark channel prior and attenuation compensation

Science.gov (United States)

Guo, Qingwen; Xue, Lulu; Tang, Ruichun; Guo, Lingrui

2017-10-01

Aimed at the two problems of underwater imaging, fog effect and color cast, an Improved Segmentation Dark Channel Prior (ISDCP) defogging method is proposed to solve the fog effects caused by physical properties of water. Due to mass refraction of light in the process of underwater imaging, fog effects would lead to image blurring. And color cast is closely related to different degree of attenuation while light with different wavelengths is traveling in water. The proposed method here integrates the ISDCP and quantitative histogram stretching techniques into the image enhancement procedure. Firstly, the threshold value is set during the refinement process of the transmission maps to identify the original mismatching, and to conduct the differentiated defogging process further. Secondly, a method of judging the propagating distance of light is adopted to get the attenuation degree of energy during the propagation underwater. Finally, the image histogram is stretched quantitatively in Red-Green-Blue channel respectively according to the degree of attenuation in each color channel. The proposed method ISDCP can reduce the computational complexity and improve the efficiency in terms of defogging effect to meet the real-time requirements. Qualitative and quantitative comparison for several different underwater scenes reveals that the proposed method can significantly improve the visibility compared with previous methods.

The Ultraviolet Attenuation Law in Backlit Spiral Galaxies

Science.gov (United States)

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

Ultra-low acoustoelectric attenuation in graphene

Science.gov (United States)

Tang, Chiu-Chun; Chen, Yung-Fu; Ling, D. C.; Chi, C. C.; Chen, Jeng-Chung

2017-03-01

We investigate the acoustoelectric properties of graphene and extract its acoustoelectric attenuation Γ as a function of the carrier density n, tuned via ionic liquid gating. Acoustoelectric effects in graphene are induced by launching surface acoustic waves (SAWs) on a piezoelectric LiNbO3 substrate. We measure the acoustoelectric current Iae through graphene and extract the SAW attenuation factor Γ as a function of n. The magnitude of Iae increases with decreasing n when the n is far from the charge neutral point (CNP). When n is tuned across the CNP, Iae first exhibits a local maximum, vanishes at the CNP, and then changes sign in accordance with the associated change in the carrier polarity. By contrast, Γ monotonically increases with decreasing n and reaches a maximum at the CNP. The extracted values of Γ, calibrated at the central frequency of 189 MHz, vary from ˜0.4 m-1 to 6.8 m-1, much smaller than the values for known two-dimensional systems. Data analysis suggests that the evolution of Iae and Γ with n manifests the electronic states of graphene. Our experimental findings provide insightful information for developing innovative graphene-based devices.

Use of two monoenergetic gamma-ray attenuation method in wood samples

International Nuclear Information System (INIS)

Mortatti, J.; Nascimento Filho, V.F. do; Barros Ferraz, E.S. de

1983-01-01

The mass attenuation coefficients for 10 wood species were determined employing the gamma attenuation technique with a single beam comprising two monoenergetics gamma energies from 137 Cs/sup(137m) Ba and 141 Am (662 and 59,6 KeV, respectively). The absorbed radiation was simultaneously measured by means of a 3'' x 3'' Nal (T1) planar solid scintillator crystal connected to a two channel gamma spectrometer. The effect of the 137 Cs/ sup(137m) Ba compton radiation on the not 241 Am counting rates were corrected. Dead time effects were desregarded, as the counting rates were always below 10 5 cpm. (Author) [pt

Prognostic significance of contrast-enhanced CT attenuation value in extrahepatic cholangiocarcinoma

Energy Technology Data Exchange (ETDEWEB)

Asayama, Yoshiki [Kyushu University, Department of Advanced Imaging and Interventional Radiology, Graduate School of Medical Sciences, Fukuoka (Japan); Nishie, Akihiro; Ishigami, Kousei; Ushijima, Yasuhiro; Takayama, Yukihisa; Okamoto, Daisuke; Fujita, Nobuhiro; Honda, Hiroshi [Kyushu University, Departments of Clinical Radiology, Fukuoka (Japan); Ohtsuka, Takao [Kyushu University, Departments of Surgery and Oncology, Fukuoka (Japan); Yoshizumi, Tomoharu [Kyushu University, Departments of Surgery and Sciences, Fukuoka (Japan); Aishima, Shinichi [Saga University, Pathology and Microbiology, Faculty of Medicine, Saga (Japan); Kyushu University, Departments of Anatomic Pathology, Graduate School of Medical Sciences, Fukuoka (Japan); Oda, Yoshinao [Kyushu University, Departments of Anatomic Pathology, Graduate School of Medical Sciences, Fukuoka (Japan)

2017-06-15

To determine whether washout characteristics of dynamic contrast-enhanced computed tomography (CT) could predict survival in patients with extrahepatic cholangiocarcinoma (EHC). This study collected 46 resected cases. All cases were examined by dynamic contrast study on multidetector-row CT. Region-of-interest measurements were obtained at the non-enhanced, portal venous phase and delayed phase in the tumour and were used to calculate the washout ratio as follows: [(attenuation value at portal venous phase CT - attenuation value at delayed enhanced CT)/(attenuation value at portal venous phase CT - attenuation value at unenhanced CT)] x 100. On the basis of the median washout ratio, we classified the cases into two groups, a high-washout group and low-washout group. Associations between overall survival and various factors including washout rates were analysed. The median washout ratio was 29.4 %. Univariate analysis revealed that a lower washout ratio, venous invasion, lymphatic permeation and lymph node metastasis were associated with shorter survival. Multivariate analysis identified the lower washout ratio as an independent prognostic factor (hazard ratio, 3.768; p value, 0.027). The washout ratio obtained from the contrast-enhanced CT may be a useful imaging biomarker for the prediction of survival of patients with EHC. (orig.)

Foot-and-mouth disease virus type O specific mutations determine RNA-dependent RNA polymerase fidelity and virus attenuation.

Science.gov (United States)

Li, Chen; Wang, Haiwei; Yuan, Tiangang; Woodman, Andrew; Yang, Decheng; Zhou, Guohui; Cameron, Craig E; Yu, Li

2018-05-01

Previous studies have shown that the FMDV Asia1/YS/CHA/05 high-fidelity mutagen-resistant variants are attenuated (Zeng et al., 2014). Here, we introduced the same single or multiple-amino-acid substitutions responsible for increased 3D pol fidelity of type Asia1 FMDV into the type O FMDV O/YS/CHA/05 infectious clone. The rescued viruses O-DA and O-DAMM are lower replication fidelity mutants and showed an attenuated phenotype. These results demonstrated that the same amino acid substitution of 3D pol in different serotypes of FMDV strains had different effects on viral fidelity. In addition, nucleoside analogues were used to select high-fidelity mutagen-resistant type O FMDV variants. The rescued mutagen-resistant type O FMDV high-fidelity variants exhibited significantly attenuated fitness and a reduced virulence phenotype. These results have important implications for understanding the molecular mechanism of FMDV evolution and pathogenicity, especially in developing a safer modified live-attenuated vaccine against FMDV. Copyright © 2018 Elsevier Inc. All rights reserved.

The Effect of Various Waste Materials' Contents on the Attenuation Level of Anti-Radiation Shielding Concrete.

Science.gov (United States)

Azeez, Ali Basheer; Mohammed, Kahtan S; Abdullah, Mohd Mustafa Al Bakri; Hussin, Kamarudin; Sandu, Andrei Victor; Razak, Rafiza Abdul

2013-10-23

Samples of concrete contain various waste materials, such as iron particulates, steel balls of used ball bearings and slags from steel industry were assessed for their anti-radiation attenuation coefficient properties. The attenuation measurements were performed using gamma spectrometer of NaI (Tl) detector. The utilized radiation sources comprised 137 Cs and ⁶⁰Co radioactive elements with photon energies of 0.662 MeV for 137 Cs and two energy levels of 1.17 and 1.33 MeV for the ⁶⁰Co. Likewise the mean free paths for the tested samples were obtained. The aim of this work is to investigate the effect of the waste loading rates and the particulate dispersive manner within the concrete matrix on the attenuation coefficients. The maximum linear attenuation coefficient (μ) was attained for concrete incorporates iron filling wastes of 30 wt %. They were of 1.12 ± 1.31×10 -3 for 137 Cs and 0.92 ± 1.57 × 10 -3 for ⁶⁰Co. Substantial improvement in attenuation performance by 20%-25% was achieved for concrete samples incorporate iron fillings as opposed to that of steel ball samples at different (5%-30%) loading rates. The steel balls and the steel slags gave much inferior values. The microstructure, concrete-metal composite density, the homogeneity and particulate dispersion were examined and evaluated using different metallographic, microscopic and measurement facilities.

Fuselage panel noise attenuation by piezoelectric switching control

International Nuclear Information System (INIS)

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

2010-01-01

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

Hippocampal NPY gene transfer attenuates seizures without affecting epilepsy-induced impairment of LTP

DEFF Research Database (Denmark)

Sørensen, Andreas T; Nikitidou, Litsa; Ledri, Marco

2009-01-01

(TLE). However, our previous studies show that recombinant adeno-associated viral (rAAV)-NPY treatment in naive rats attenuates long-term potentiation (LTP) and transiently impairs hippocampal learning process, indicating that negative effect on memory function could be a potential side effect of NPY...... is significantly attenuated in vitro. Importantly, transgene NPY overexpression has no effect on short-term synaptic plasticity, and does not further compromise LTP in kindled animals. These data suggest that epileptic seizure-induced impairment of memory function in the hippocampus may not be further affected...... injected with rAAV-NPY, we show that rapid kindling-induced hippocampal seizures in vivo are effectively suppressed as compared to rAAV-empty injected (control) rats. Six to nine weeks later, basal synaptic transmission and short-term synaptic plasticity are unchanged after rapid kindling, while LTP...

X-ray attenuation of the liver and kidney in cats considered at varying risk of hepatic lipidosis.

Science.gov (United States)

Lam, Richard; Niessen, Stijn J; Lamb, Christopher R

2014-01-01

X-ray attenuation of the liver has been measured using computed tomography (CT) and reported to decrease in cats with experimentally induced hepatic lipidosis. To assess the clinical utility of this technique, medical records and noncontrast CT scans of a series of cats were retrospectively reviewed. A total of 112 cats met inclusion criteria and were stratified into three hepatic lipidosis risk groups. Group 1 cats were considered low-risk based on no history of inappetence or weight loss, and normal serum chemistry values; Group 2 cats were considered intermediate risk based on weight loss, serum hepatic enzymes above normal limits, or reasonably controlled diabetes mellitus; and Group 3 cats were considered high risk based on poorly controlled diabetes mellitus due to hypersomatotropism. Mean CT attenuation values (Hounsfield units, HU) were measured using regions of interest placed within the liver and cranial pole of the right kidney. Hepatic and renal attenuation were weakly positively correlated with each other (r = 0.2, P = 0.03) and weakly negatively correlated with body weight (r = -0.21, P = 0.05, and r = -0.34, P = 0.001, respectively). Mean (SD) hepatic and renal cortical attenuation values were 70.7 (8.7) HU and 49.6 (9.2) HU for Group 1 cats, 71.4 (7.9) HU and 48.6 (9.1) HU for Group 2, and 68.9 (7.6) HU and 47.6 (7.2) HU for Group 3. There were no significant differences in hepatic or renal attenuation among groups. Findings indicated that CT measures of X-ray attenuation in the liver and kidney may not be accurate predictors of naturally occurring hepatic lipidosis in cats. © 2013 American College of Veterinary Radiology.

Silibinin attenuates sulfur mustard analog-induced skin injury by targeting multiple pathways connecting oxidative stress and inflammation.

Directory of Open Access Journals (Sweden)

Neera Tewari-Singh

Full Text Available Chemical warfare agent sulfur mustard (HD inflicts delayed blistering and incapacitating skin injuries. To identify effective countermeasures against HD-induced skin injuries, efficacy studies were carried out employing HD analog 2-chloroethyl ethyl sulfide (CEES-induced injury biomarkers in skin cells and SKH-1 hairless mouse skin. The data demonstrate strong therapeutic efficacy of silibinin, a natural flavanone, in attenuating CEES-induced skin injury and oxidative stress. In skin cells, silibinin (10 µM treatment 30 min after 0.35/0.5 mM CEES exposure caused a significant (p90%, and activation of transcription factors NF-κB and AP-1 (complete reversal. Similarly, silibinin treatment was also effective in attenuating CEES-induced oxidative stress measured by 4-hydroxynonenal and 5,5-dimethyl-2-(8-octanoic acid-1-pyrolline N-oxide protein adduct formation, and 8-oxo-2-deoxyguanosine levels. Since our previous studies implicated oxidative stress, in part, in CEES-induced toxic responses, the reversal of CEES-induced oxidative stress and other toxic effects by silibinin in this study indicate its pleiotropic therapeutic efficacy. Together, these findings support further optimization of silibinin in HD skin toxicity model to develop a novel effective therapy for skin injuries by vesicants.

Study characteristics of new concrete mixes and their mechanical, physical, and gamma radiation attenuation features

Energy Technology Data Exchange (ETDEWEB)

El-Samrah, Moamen G.; Abdel-Rahman, Mohamed A.E. [Nuclear Engineering Department, Military Technical College Kobry El-kobbah, Cairo (Egypt); Kany, Amr M.I. [Physics Department, Faculty of Science, Al-Azhar University, Cairo (Egypt)

2018-02-01

Ordinary concrete and those of different compositions are regarded as suitable material in many applications concerning with gamma and neutron radiation shielding purposes. They are widely used in nuclear power plant, medical facilities, nuclear shelters, and for radioactive materials transportation as well as storage of radioactive wastes. In this study four different concrete mixes were prepared with the following different types of coarse aggregates: dolomite, barite, goethite, and steel slag. The effect of changes in the fine aggregates, selected to be 50 % local sand and 50 % limonite with addition of 10 % silica fume (SF) and 10 % fly ash (FA) by replacement of the total cement weight, on the performance of the samples was also investigated. To examine the performance of such samples for radiation shielding applications, a set of physical, mechanical, and radiation attenuation properties was studied and compared with those of ordinary concrete. This investigation includes compressive strength, slump test, bulk density, ultrasonic pulse velocity test, and gamma rays attenuation measurements for the different samples. A verification of the experimental results concerning the radiation attenuation measurements was performed using WinXcom program (Version 3.1). The experimental results revealed that all concrete mixes; goethite-limonite concrete (G.L), barite-limonite concrete (B.L), steel slag-limonite concrete (S.L) and dolomite concrete (D.C) have good physical and mechanical properties that successfully satisfying them as high performance concretes. In addition the barite-limonite and the steel slag-limonite have the higher γ-ray attenuation coefficients at low and high energy range and hence have a better radiation shielding. The obtained results from WinXcom program calculations showed a good agreement with the experimental results concerning γ-ray attenuation measurements for the studied concrete mixes. (copyright 2018 WILEY-VCH Verlag GmbH and Co. KGa

Thermal expansion and density measurements of molten and solid materials at high temperatures by the gamma attenuation technique

International Nuclear Information System (INIS)

Drotning, W.D.

1979-05-01

An apparatus is described for the measurement of the density and thermal expansion of molten materials to 3200 0 K using the gamma attenuation technique. The precision of the experimental technique was analytically examined for both absolute and relative density determinations. Three analytical expressions used to reduce data for liquid density determinations were evaluated for their precision. Each allows use of a different set of input data parameters, which can be chosen based on experimental considerations. Using experimentally reasonable values for the precision of the parameters yields a similar resultant density precision from the three methods, on the order of 0.2%. The analytical method for measurements of the linear thermal expansion of solids by the gamma method is also described. To demonstrate the use of the technique on reasonably well-characterized systems, data are presented for (1) the density and thermal expansion of molten tin, lead, and aluminum to 1300 0 K, (2) the thermal expansion of solid aluminum to the melting point, and (3) the thermal expansion of a low melting point glass through the transition temperature and melting region. The data agree very well with published results using other methods where such published data exist

Challenging previous conceptions of vegetarianism and eating disorders.

Science.gov (United States)

Fisak, B; Peterson, R D; Tantleff-Dunn, S; Molnar, J M

2006-12-01

The purpose of this study was to replicate and expand upon previous research that has examined the potential association between vegetarianism and disordered eating. Limitations of previous research studies are addressed, including possible low reliability of measures of eating pathology within vegetarian samples, use of only a few dietary restraint measures, and a paucity of research examining potential differences in body image and food choice motives of vegetarians versus nonvegetarians. Two hundred and fifty-six college students completed a number of measures of eating pathology and body image, and a food choice motives questionnaire. Interestingly, no significant differences were found between vegetarians and nonvegetarians in measures of eating pathology or body image. However, significant differences in food choice motives were found. Implications for both researchers and clinicians are discussed.