Profiles of equilibrium constants for self-association of aromatic molecules.

Science.gov (United States)

Beshnova, Daria A; Lantushenko, Anastasia O; Davies, David B; Evstigneev, Maxim P

2009-04-28

Analysis of the noncovalent, noncooperative self-association of identical aromatic molecules assumes that the equilibrium self-association constants are either independent of the number of molecules (the EK-model) or change progressively with increasing aggregation (the AK-model). The dependence of the self-association constant on the number of molecules in the aggregate (i.e., the profile of the equilibrium constant) was empirically derived in the AK-model but, in order to provide some physical understanding of the profile, it is proposed that the sources for attenuation of the equilibrium constant are the loss of translational and rotational degrees of freedom, the ordering of molecules in the aggregates and the electrostatic contribution (for charged units). Expressions are derived for the profiles of the equilibrium constants for both neutral and charged molecules. Although the EK-model has been widely used in the analysis of experimental data, it is shown in this work that the derived equilibrium constant, K(EK), depends on the concentration range used and hence, on the experimental method employed. The relationship has also been demonstrated between the equilibrium constant K(EK) and the real dimerization constant, K(D), which shows that the value of K(EK) is always lower than K(D).

Attenuated radon transform: theory and application in medicine and biology

Energy Technology Data Exchange (ETDEWEB)

Gullberg, G.T.

1979-06-01

A detailed analysis is given of the properties of the attenuated Radon transform and of how increases in photon attenuation influence the numerical accuracy and computation efficiency of iterative and convolution algorithms used to determine its inversion. The practical applications for this work involve quantitative assessment of the distribution of injected radiopharmaceuticals and radionuclides in man and animals for basic physiological and biochemical studies as well as clinical studies in nuclear medicine. A mathematical structure is developed using function theory and the theory of linear operators on Hilbert spaces which lends itself to better understanding the spectral properties of the attenuated Radon transform. The continuous attenuated Radon transform reduces to a matrix operator for discrete angular and lateral sampling, and the reconstruction problem reduces to a system of linear equations. For the situation of variable attenuation coefficient frequently found in nuclear medicine applications of imaging the heart and chest, the procedure developed in this thesis involves iterative techniques of performing the generalized inverse. For constant attenuation coefficient less than 0.15 cm/sup -1/, convolution methods can reliably reconstruct a 30 cm object with 0.5 cm resolution. However, for high attenuation coefficients or for the situation where there is variable attenuation such as reconstruction of distribution of isotopes in the heart, iterative techniques developed in this thesis give the best results. (ERB)

Viscosity and attenuation of sound wave in high density deuterium

International Nuclear Information System (INIS)

Inoue, Kazuko; Ariyasu, Tomio

1985-01-01

The penetration of low frequency sound wave into the fuel deuterium is discussed as for laser fusion. The sound velocity and the attenuation constant due to viscosity are calculated for high density (n = 10 24 -- 10 27 cm -3 , T = 10 -1 -- 10 4 eV) deuterium. The shear viscosity of free electron gas and the bulk viscosity due to ion-ion interaction mainly contribute to the attenuation of sound wave. The sound wave of the frequency below 10 10 Hz can easily penetrate through the compressed fuel deuterium of diameter 1 -- 10 3 μm. (author)

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

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...

Optical constants and self-assembly of phenylene ethynylene oligomer monolayers

DEFF Research Database (Denmark)

Marx, E.; Walzer, Karsten; Less, R.J.

2004-01-01

This paper studies the self-assembly on gold surfaces of 1,4-ethynylphenyl-4'-ethynylphenyl-2'-nitro-1-benzenedithiolate (EP2NO(2)), a substituted phenylene ethynylene trimer with applications in molecular electronics. We develop an ellipsometric technique to measure the optical constants...... of these self-assembled monolayers, and we also use attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy and scanning tunneling microscopy (STM) to confirm the structure of the films....

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

Inferring global upper-mantle shear attenuation structure by waveform tomography using the spectral element method

Science.gov (United States)

Karaoǧlu, Haydar; Romanowicz, Barbara

2018-06-01

We present a global upper-mantle shear wave attenuation model that is built through a hybrid full-waveform inversion algorithm applied to long-period waveforms, using the spectral element method for wavefield computations. Our inversion strategy is based on an iterative approach that involves the inversion for successive updates in the attenuation parameter (δ Q^{-1}_μ) and elastic parameters (isotropic velocity VS, and radial anisotropy parameter ξ) through a Gauss-Newton-type optimization scheme that employs envelope- and waveform-type misfit functionals for the two steps, respectively. We also include source and receiver terms in the inversion steps for attenuation structure. We conducted a total of eight iterations (six for attenuation and two for elastic structure), and one inversion for updates to source parameters. The starting model included the elastic part of the relatively high-resolution 3-D whole mantle seismic velocity model, SEMUCB-WM1, which served to account for elastic focusing effects. The data set is a subset of the three-component surface waveform data set, filtered between 400 and 60 s, that contributed to the construction of the whole-mantle tomographic model SEMUCB-WM1. We applied strict selection criteria to this data set for the attenuation iteration steps, and investigated the effect of attenuation crustal structure on the retrieved mantle attenuation structure. While a constant 1-D Qμ model with a constant value of 165 throughout the upper mantle was used as starting model for attenuation inversion, we were able to recover, in depth extent and strength, the high-attenuation zone present in the depth range 80-200 km. The final 3-D model, SEMUCB-UMQ, shows strong correlation with tectonic features down to 200-250 km depth, with low attenuation beneath the cratons, stable parts of continents and regions of old oceanic crust, and high attenuation along mid-ocean ridges and backarcs. Below 250 km, we observe strong attenuation in the

Radiation induced time dependent attenuation in a fiber

International Nuclear Information System (INIS)

Kelly, R.E.; Lyons, P.B.; Looney, L.D.

1985-01-01

Characteristics describing the time dependent attenuation coefficient of an optical fiber during and following a very short and intense radiation pulse are analyzed. This problem is important for transmission applications when the fiber is subjected to gamma, electron, or neutron beams. Besides time, the attenuation coefficient is a function of temperature, dose rate, dose, nature of the radiation (n, e, γ), fiber composition and purity, pre-existing solid state defects, and wavelength of the transmitted signal. The peak attenuation for a given fiber is mainly determined by the dose rate and pulse length, but temperature and strain (or athermal) annealing also contribute to a partial recovery during the pulse duration. The peak attenuation per unit dose appears to be smaller at high doses, perhaps caused by particle track overlap, which produces a saturation effect. After pulse termination, the attenuation coefficient tends to recover towards its pre-radiation value at different rates, depending upon the factors mentioned above. In particular, ionized electrons relax back to the positive lattice ions at a rate which depends upon initial separation distance and temperature. The initial separation distance is a function of beam energy. Some electrons will encounter a trap in the lattice and may recombine by quantum mechanical tunneling or be removed by photons (hence, absorption). Besides ionization, radiation may induce lattice displacements which in turn produce additional absorption centers. The displacement contribution has a different time constant than that associated with ionization. These topics, as they influence fiber characteristics, are discussed, along with supporting experimental data

Flexural wave attenuation in a sandwich beam with viscoelastic periodic cores

Science.gov (United States)

Guo, Zhiwei; Sheng, Meiping; Pan, Jie

2017-07-01

The flexural-wave attenuation performance of traditional constraint-layer damping in a sandwich beam is improved by using periodic constrained-layer damping (PCLD), where the monolithic viscoelastic core is replaced with two periodically alternating viscoelastic cores. Closed-form solutions of the wave propagation constants of the infinite periodic sandwich beam and the forced response of the corresponding finite sandwich structure are theoretically derived, providing computational support on the analysis of attenuation characteristics. In a sandwich beam with PCLD, the flexural waves can be attenuated by both Bragg scattering effect and damping effect, where the attenuation level is mainly dominated by Bragg scattering in the band-gaps and by damping in the pass-bands. Affected by these two effects, when the parameters of periodic cores are properly selected, a sandwich beam with PCLD can effectively reduce vibrations of much lower frequencies than that with traditional constrained-layer damping. The effects of the parameters of viscoelastic periodic cores on band-gap properties are also discussed, showing that the average attenuation in the desired frequency band can be maximized by tuning the length ratio and core thickness to proper values. The research in this paper could possibly provide useful information for the researches and engineers to design damping structures.

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.

Attenuation of photon beams from radionuclides. Pt. 6

International Nuclear Information System (INIS)

Dorner, R.; Vogt, H.G.

1982-04-01

Point kernel shielding calculations have been performed for water for the photons of radioactive nuclides, comprising gamma rays, characteristic X-rays, annihilation photons as well as internal and external bremsstrahlung. The calculations refer to an isotropic point source and an infinite homogeneous medium. The results are presented for 137 radionuclides by tables of dose rate constants and sets of figures of the reciprocal attenuation factor S -1 . The shielding curves cover the range of 10 -8 -1 <1 and water thicknesses up to 340 cm. (orig./HP)

Attenuation correction of myocardial SPECT images with X-ray CT. Effects of registration errors between X-ray CT and SPECT

International Nuclear Information System (INIS)

Takahashi, Yasuyuki; Murase, Kenya; Mochizuki, Teruhito; Motomura, Nobutoku

2002-01-01

Attenuation correction with an X-ray CT image is a new method to correct attenuation on SPECT imaging, but the effect of the registration errors between CT and SPECT images is unclear. In this study, we investigated the effects of the registration errors on myocardial SPECT, analyzing data from a phantom and a human volunteer. Registerion (fusion) of the X-ray CT and SPECT images was done with standard packaged software in three dimensional fashion, by using linked transaxial, coronal and sagittal images. In the phantom study, and X-ray CT image was shifted 1 to 3 pixels on the x, y and z axes, and rotated 6 degrees clockwise. Attenuation correction maps generated from each misaligned X-ray CT image were used to reconstruct misaligned SPECT images of the phantom filled with 201 Tl. In a human volunteer, X-ray CT was acquired in different conditions (during inspiration vs. expiration). CT values were transferred to an attenuation constant by using straight lines; an attenuation constant of 0/cm in the air (CT value=-1,000 HU) and that of 0.150/cm in water (CT value=0 HU). For comparison, attenuation correction with transmission CT (TCT) data and an external γ-ray source ( 99m Tc) was also applied to reconstruct SPECT images. Simulated breast attenuation with a breast attachment, and inferior wall attenuation were properly corrected by means of the attenuation correction map generated from X-ray CT. As pixel shift increased, deviation of the SPECT images increased in misaligned images in the phantom study. In the human study, SPECT images were affected by the scan conditions of the X-ray CT. Attenuation correction of myocardial SPECT with an X-ray CT image is a simple and potentially beneficial method for clinical use, but accurate registration of the X-ray CT to SPECT image is essential for satisfactory attenuation correction. (author)

Theoretical study of temperature dependent acoustic attenuation and non-linearity parameters in alkali metal hydride and deuteride

Energy Technology Data Exchange (ETDEWEB)

Singh, Rishi Pal [Department of Physics, Banaras Hindu University, Varanasi 221005 (India); Singh, Rajendra Kumar, E-mail: rksingh_17@rediffmail.com [Department of Physics, Banaras Hindu University, Varanasi 221005 (India)

2010-11-01

Temperature dependence of acoustic attenuation and non-linearity parameters in lithium hydride and lithium deuteride have been studied for longitudinal and shear modes along various crystallographic directions of propagation in a wide temperature range. Lattice parameter and repulsive parameters have been used as input data and interactions up to next nearest neighbours have been considered to calculate second and third order elastic constants which in turn have been used for evaluating acoustic attenuation and related parameters. The results have been discussed and compared with available data. It is hoped that the present results will serve to stimulate the determination of the acoustic attenuation of these compounds at different temperatures.

Implementing Monitored Natural Attenuation and Expediting Closure at Fuel-Release Sites

Science.gov (United States)

2004-08-01

gasoline, kerosene, diesel, and jet fuel (e.g., Jamison et al., 1975; Atlas , 1981, 1984, and 1988; Young, 1984; Bartha , 1986; Wilson et al., 1986 and...Supporting data. Gas Research Institute, Chicago, Illinois. Atlas , R. M. 1981. Microbial degradation of petroleum hydrocarbons - an Environmental... Microbial Ecology 12:155-172 Battelle. 1984. Chemical Attenuation Rates Coefficients, and Constants in Leachate Migration. Vol I: Critical Review

An ice-sheet-wide framework for englacial attenuation from ice-penetrating radar data

Science.gov (United States)

Jordan, T. M.; Bamber, J. L.; Williams, C. N.; Paden, J. D.; Siegert, M. J.; Huybrechts, P.; Gagliardini, O.; Gillet-Chaulet, F.

2016-07-01

Radar inference of the bulk properties of glacier beds, most notably identifying basal melting, is, in general, derived from the basal reflection coefficient. On the scale of an ice sheet, unambiguous determination of basal reflection is primarily limited by uncertainty in the englacial attenuation of the radio wave, which is an Arrhenius function of temperature. Existing bed-returned power algorithms for deriving attenuation assume that the attenuation rate is regionally constant, which is not feasible at an ice-sheet-wide scale. Here we introduce a new semi-empirical framework for deriving englacial attenuation, and, to demonstrate its efficacy, we apply it to the Greenland Ice Sheet. A central feature is the use of a prior Arrhenius temperature model to estimate the spatial variation in englacial attenuation as a first guess input for the radar algorithm. We demonstrate regions of solution convergence for two input temperature fields and for independently analysed field campaigns. The coverage achieved is a trade-off with uncertainty and we propose that the algorithm can be "tuned" for discrimination of basal melt (attenuation loss uncertainty ˜ 5 dB). This is supported by our physically realistic ( ˜ 20 dB) range for the basal reflection coefficient. Finally, we show that the attenuation solution can be used to predict the temperature bias of thermomechanical ice sheet models and is in agreement with known model temperature biases at the Dye 3 ice core.

Elongational flow of polymer melts at constant strain rate, constant stress and constant force

Science.gov (United States)

Wagner, Manfred H.; Rolón-Garrido, Víctor H.

2013-04-01

Characterization of polymer melts in elongational flow is typically performed at constant elongational rate or rarely at constant tensile stress conditions. One of the disadvantages of these deformation modes is that they are hampered by the onset of "necking" instabilities according to the Considère criterion. Experiments at constant tensile force have been performed even more rarely, in spite of the fact that this deformation mode is free from necking instabilities and is of considerable industrial relevance as it is the correct analogue of steady fiber spinning. It is the objective of the present contribution to present for the first time a full experimental characterization of a long-chain branched polyethylene melt in elongational flow. Experiments were performed at constant elongation rate, constant tensile stress and constant tensile force by use of a Sentmanat Extensional Rheometer (SER) in combination with an Anton Paar MCR301 rotational rheometer. The accessible experimental window and experimental limitations are discussed. The experimental data are modelled by using the Wagner I model. Predictions of the steady-start elongational viscosity in constant strain rate and creep experiments are found to be identical, albeit only by extrapolation of the experimental data to Hencky strains of the order of 6. For constant stress experiments, a minimum in the strain rate and a corresponding maximum in the elongational viscosity is found at a Hencky strain of the order of 3, which, although larger than the steady-state value, follows roughly the general trend of the steady-state elongational viscosity. The constitutive analysis also reveals that constant tensile force experiments indicate a larger strain hardening potential than seen in constant elongation rate or constant tensile stress experiments. This may be indicative of the effect of necking under constant elongation rate or constant tensile stress conditions according to the Considère criterion.

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

Scaling of nuclear modification factors for hadrons and light nuclei

Energy Technology Data Exchange (ETDEWEB)

Zhou, C.S. [Chinese Academy of Sciences, Shanghai Institute of Applied Physics, Shanghai (China); University of Chinese Academy of Sciences, Beijing (China); Ma, Y.G. [Chinese Academy of Sciences, Shanghai Institute of Applied Physics, Shanghai (China); ShanghaiTech University, Shanghai (China); Zhang, S. [Chinese Academy of Sciences, Shanghai Institute of Applied Physics, Shanghai (China)

2016-12-15

The number of constituent quarks (NCQ) scaling for hadrons and the number of constituent nucleons (NCN) scaling for light nuclei are proposed for nuclear modification factors (R{sub cp}) of hadrons and light nuclei, respectively, according to the experimental investigations in relativistic heavy-ion collisions. Based on the coalescence mechanism the scalings are performed for pions and protons at the quark level, and for light nuclei d(anti d) and {sup 3}He at the nucleonic level, respectively, formed in Au+Au and Pb+Pb collisions, and a nice scaling behaviour emerges. The NCQ or NCN scaling law of R{sub cp} can be, respectively, taken as a probe for the quark or nucleon coalescence mechanism for the formation of hadron or light nuclei in relativistic heavy-ion collisions. (orig.)

Constant physics and characteristics of fundamental constant

International Nuclear Information System (INIS)

Tarrach, R.

1998-01-01

We present some evidence which supports a surprising physical interpretation of the fundamental constants. First, we relate two of them through the renormalization group. This leaves as many fundamental constants as base units. Second, we introduce and a dimensional system of units without fundamental constants. Third, and most important, we find, while interpreting the units of the a dimensional system, that is all cases accessible to experimentation the fundamental constants indicate either discretization at small values or boundedness at large values of the corresponding physical quantity. (Author) 12 refs

Use of batch and column methodologies to assess utility waste leaching and subsurface chemical attenuation

International Nuclear Information System (INIS)

Zachara, J.M.; Streile, G.P.

1991-05-01

Waste leaching and chemical attenuation involve geochemical reactions between immobile solid surfaces in the waste or in other porous media and dissolved solutes in the mobile fluid phase. Because the geochemical reactions occur along with water flow, the question often arises whether waste leaching and chemical attenuation are best studied under static or dynamic conditions. To answer this question, the scientific literature was reviewed to identify how static (batch) and dynamic (column) approaches have been applied to obtain data on waste leaching and chemical attenuation and the types of information each technique has provided. This review made it possible to both (1) assess the specific merits of the batch and column experimental techniques and (2) develop an integrated research strategy for employing these techniques to quantify leaching and chemical attenuation processes under conditions relevant to the field. This review led to the conclusion that batch systems are best suited to systematically establishing the specific geochemical reactions involved in leaching and attenuation, obtaining thermodynamic and kinetic constants, and identifying the manifestation of these reactions in wastes or natural subsurface materials. 184 refs., 5 figs., 4 tabs

Lithium-doped hydroxyapatite nano-composites: Synthesis, characterization, gamma attenuation coefficient and dielectric properties

Science.gov (United States)

Badran, H.; Yahia, I. S.; Hamdy, Mohamed S.; Awwad, N. S.

2017-01-01

Lithium-hydroxyapatite (0, 1, 5, 10, 20, 30 and 40 wt% Li-HAp) nano-composites were synthesized by sol-gel technique followed by microwave-hydrothermal treatment. The composites were characterized by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) and Raman techniques. Gamma attenuation coefficient and the dielectric properties for all composites were investigated. The crystallinity degree of Li-doped HAp was higher than that of un-doped HAp. Gamma attenuation coefficient values increased from 0.562 cm-1 for 0 wt% Li-HAp to 2.190 cm-1 for 40 wt% Li-HAp. The alternating current conductivity increased with increasing frequency. The concentration of Li affect the values of dielectric constant where Li doped HAp of low dielectric constant can have an advantage for healing in bone fractures. The calcium to phosphorus ratio decreased from 1.43 to 1.37 with the addition of lithium indicating the Ca deficiency in the studied composites. Our findings lead to the conclusion that Li-HAp is a new nano-composite useful for medical applications and could be doped with gamma shield materials.

Sound attenuation and absorption by anisotropic fibrous materials: Theoretical and experimental study

Science.gov (United States)

Bravo, Teresa; Maury, Cédric

2018-03-01

This paper describes analytical and experimental studies carried out to examine the attenuation and absorption properties of rigidly-backed fibrous anisotropic materials in contact with a uniform mean flow. The aim is to provide insights for the development of non-locally reacting wall-treatments able to dissipate the noise induced by acoustic excitations over in-duct or external lining systems. A model of sound propagation in anisotropic bulk-reacting liners is presented that fully accounts for anisotropic losses due to heat conduction, viscous dissipation and diffusion processes along and across the material fibres as well as for the convective effect of an external flow. The propagation constant for the least attenuated mode of the coupled system is obtained using a simulated annealing search method. The predicted acoustical performance is validated in the no-flow case for a wide range of fibre diameters. They are assessed against impedance tube and free-field pressure-velocity measurements of the normal incidence absorption coefficient and surface impedance. Parametric studies are then conducted to determine the key constitutive parameters such as the fibres orientation or the amount of anisotropy that mostly influence the axial attenuation or the normal absorption. They are supported by a low-frequency approximation to the axial attenuation under a low-speed flow.

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

Simultaneous reconstruction of attenuation and activity in ToF PET/MRI with additional transmission data

Energy Technology Data Exchange (ETDEWEB)

D’Hoe, Ester [MEDISIP Medical Imaging and Signal Processing Group, Ghent University, IBBT-IBiTech, iMinds Medical IT, Ghent (Belgium); Department of Nuclear Medicine, Vrije Universiteit Brussel, Brussels (Belgium); Mollet, Pieter; Mikhaylova, Ekaterina [MEDISIP Medical Imaging and Signal Processing Group, Ghent University, IBBT-IBiTech, iMinds Medical IT, Ghent (Belgium); Defrise, Michel [Department of Nuclear Medicine, Vrije Universiteit Brussel, Brussels (Belgium); Vandenberghe, Stefaan [MEDISIP Medical Imaging and Signal Processing Group, Ghent University, IBBT-IBiTech, iMinds Medical IT, Ghent (Belgium)

2015-05-18

In Time-of-Flight PET/MRI systems accurate attenuation correction, based on the MRI image, is not straight forward. An alternative is attenuation correction based on emission data only. This is for instance done by simultaneous reconstruction of attenuation and activity with the MLAA algorithm, but the method as originally proposed has certain limits. The attenuation can only be determined up to a constant and in regions of low tracer uptake, the method results in less accurate attenuation values. An adapted MLAA algorithm has been proposed to overcome this issues and was successfully applied on simulation studies. The so called MLAA+ algorithm uses regular PET emission data as well as transmission data. This transmission data is acquired after insertion of an annulus shaped transmission source into the scanner bore. The Time-of-Flight information allows to separate transmission and emission data in a simultaneous acquisition. With the transmission data, an MLTR-based reference attenuation image is reconstructed. Afterwards, this attenuation image is used in the MLAA+ simultaneous reconstruction of attenuation and emission as a reference. We here propose the results of the reconstruction of patient data, based on the MLAA+ algorithm. In total, seven patients were scanned in a sequential PET/MRI scanner and afterwards in a CT scanner. The CT scan is used as an attenuation map to reconstruct the PET emission data with the well established MLEM algorithm. This reconstruction can be seen as the gold standard to which we can compare the MLAA and MLAA+ reconstructions. A preliminary study on one patient indicates that the MLAA+ algorithm results in better reconstructed emission and attenuation images as compared to the MLAA algorithm. If we compare the MLAA+ method to the gold standard, there is still room for improvement.

Simultaneous reconstruction of attenuation and activity in ToF PET/MRI with additional transmission data

International Nuclear Information System (INIS)

D’Hoe, Ester; Mollet, Pieter; Mikhaylova, Ekaterina; Defrise, Michel; Vandenberghe, Stefaan

2015-01-01

In Time-of-Flight PET/MRI systems accurate attenuation correction, based on the MRI image, is not straight forward. An alternative is attenuation correction based on emission data only. This is for instance done by simultaneous reconstruction of attenuation and activity with the MLAA algorithm, but the method as originally proposed has certain limits. The attenuation can only be determined up to a constant and in regions of low tracer uptake, the method results in less accurate attenuation values. An adapted MLAA algorithm has been proposed to overcome this issues and was successfully applied on simulation studies. The so called MLAA+ algorithm uses regular PET emission data as well as transmission data. This transmission data is acquired after insertion of an annulus shaped transmission source into the scanner bore. The Time-of-Flight information allows to separate transmission and emission data in a simultaneous acquisition. With the transmission data, an MLTR-based reference attenuation image is reconstructed. Afterwards, this attenuation image is used in the MLAA+ simultaneous reconstruction of attenuation and emission as a reference. We here propose the results of the reconstruction of patient data, based on the MLAA+ algorithm. In total, seven patients were scanned in a sequential PET/MRI scanner and afterwards in a CT scanner. The CT scan is used as an attenuation map to reconstruct the PET emission data with the well established MLEM algorithm. This reconstruction can be seen as the gold standard to which we can compare the MLAA and MLAA+ reconstructions. A preliminary study on one patient indicates that the MLAA+ algorithm results in better reconstructed emission and attenuation images as compared to the MLAA algorithm. If we compare the MLAA+ method to the gold standard, there is still room for improvement.

Cosmological Hubble constant and nuclear Hubble constant

International Nuclear Information System (INIS)

Horbuniev, Amelia; Besliu, Calin; Jipa, Alexandru

2005-01-01

The evolution of the Universe after the Big Bang and the evolution of the dense and highly excited nuclear matter formed by relativistic nuclear collisions are investigated and compared. Values of the Hubble constants for cosmological and nuclear processes are obtained. For nucleus-nucleus collisions at high energies the nuclear Hubble constant is obtained in the frame of different models involving the hydrodynamic flow of the nuclear matter. Significant difference in the values of the two Hubble constant - cosmological and nuclear - is observed

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)

Infrared optical constants of aqueous sulfate-nitrate-ammonium multi-component tropospheric aerosols from attenuated total reflectance measurements: Part II. An examination of mixing rules

International Nuclear Information System (INIS)

Boer, Gregory J.; Sokolik, Irina N.; Martin, Scot T.

2007-01-01

We examine the performance of several mixing rules that are commonly used in modeling optical constants of aerosol mixtures either in remote sensing or radiation transfer/climate studies employing the new refractive index data reported in Part I. We demonstrate that the optical constants of the considered mixtures are not accurately modeled using pure solute optical constants (e.g., ammonium sulfate optical constants and the optical constants of pure water) due to the complex ion-ion and ion-water interactions. On the other hand, we do find that ternary and quaternary mixtures can be well modeled by applying the mixing rules to lower order multi-component optical constants data, e.g., binary data to determine ternary optical constants, or binary and ternary data to determine quaternary optical constants. By using lower order optical constants data sets, much of the ion-ion and ion-water effects are captured. Both mass-fraction and volume-fraction weighting of the 'component' optical constants yield satisfactory results, performing as well or better than the more complicated mixing rules. These findings will be of practical use in remote sensing and radiation transfer/climate studies as well as help guide the decision on what optical constants measurements will be required

Evaluation of visual stress symptoms in age-matched dyslexic, Meares-Irlen syndrome and normal adults.

Science.gov (United States)

Alanazi, Mana A; Alanazi, Saud A; Osuagwu, Uchechukwu L

2016-01-01

To examine the prevalence of dyslexia and Meares-Irlen syndrome (MIS) among female students and determine their level of visual stress in comparison with normal subjects. A random sample of 450 female medical students of King Saud University Riyadh (age range, 18-30y) responded to a wide range of questions designed to accomplish the aims of this study. The detailed questionnaire consisted of 54 questions with 12 questions enquiring on ocular history and demography of participants while 42 questions were on visual symptoms. Items were categorized into critical and non-critical questions (CQ and NCQ) and were rated on four point Likert scale. Based on the responses obtained, the subjects were grouped into normal (control), dyslexic with or without MIS (Group 1) and subjects with MIS only (Group 2). Responses were analysed as averages and mean scores were calculated and compared between groups using one way analysis of variance to evaluate total visual stress score (TVSS=NCQ+CQ), critical and non-critical visual stress scores. The relationship between categorical variables such as age, handedness and condition were assessed with Chi-square test. The completion rate was 97.6% and majority of the respondents (92%) were normal readers, 2% dyslexic and 6% had MIS. They were age-matched. More than half of the participants had visited an eye care practitioner in the last 2y. About 13% were recommended eye exercises and one participant experienced pattern glare. Hand preference was not associated with any condition but Group 1 subjects (3/9, 33%) were significantly more likely to be diagnosed of lazy eye than Group 2 (2/27, 7%) and control (27/414, 7%) subjects. The mean±SD of TVSS responses were 63±14 and it was 44±9 for CQ and 19±5 for NCQ. Responses from all three variables were normally distributed but the CQ responses were on the average more positive (82%) in Group 2 and less positive (46%) in Group 1 than control. With NCQ, the responses were equally less positive

Attenuation of thermal neutrons by an imperfect single crystal

Energy Technology Data Exchange (ETDEWEB)

Naguib, K.; Adib, M. [National Research Centre, Cairo (Egypt). Reactor and Neutron Physics Dept.

1996-06-14

A semi-empirical formula is given which allows one to calculate the total thermal cross section of an imperfect single crystal as a function of crystal constants, temperature and neutron energy E, in the energy range between 3 meV and 10 eV. The formula also includes the contribution of the parasitic Bragg scattering to the total cross section that takes into account the crystal mosaic spread value and its orientation with respect to the neutron beam direction. A computer program (ISCANF) was developed to calculate the total attenuation of neutrons using the proposed formula. The ISCANF program was applied to investigate the neutron attenuation through a copper single crystal. The calculated values of the neutron transmission through the imperfect copper single crystal were fitted to the measured ones in the energy range 3-40 meV at different crystal orientations. The result of fitting shows that use of the computer program ISCANF allows one to predict the behaviour of the total cross section of an imperfect copper single crystal for the whole energy range. (author).

Attenuation of thermal neutrons by an imperfect single crystal

Science.gov (United States)

Naguib, K.; Adib, M.

1996-06-01

A semi-empirical formula is given which allows one to calculate the total thermal cross section of an imperfect single crystal as a function of crystal constants, temperature and neutron energy E, in the energy range between 3 meV and 10 eV. The formula also includes the contribution of the parasitic Bragg scattering to the total cross section that takes into account the crystal mosaic spread value and its orientation with respect to the neutron beam direction. A computer program (ISCANF) was developed to calculate the total attenuation of neutrons using the proposed formula. The ISCANF program was applied to investigate the neutron attenuation through a copper single crystal. The calculated values of the neutron transmission through the imperfect copper single crystal were fitted to the measured ones in the energy range 3 - 40 meV at different crystal orientations. The result of fitting shows that use of the computer program ISCANF allows one to predict the behaviour of the total cross section of an imperfect copper single crystal for the whole energy range.

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)

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

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

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)

Attenuation characteristics of materials used in radiation protection as radiation shielding

International Nuclear Information System (INIS)

Almeida Junior, Airton T.; Araujo, F.G.S.; Nogueira, M.S.; Santos, M.A.P.

2013-01-01

Crystal glass has been widely used as shielding material in gamma radiation sources as well as x-ray generating equipment to replace the plumbiferous glass, in order to minimize exposure to individuals. In this work, ten plates of crystal glass, with dimensions of 20cm x 20cm and range of thicknesses from 0.5 to 2.0 cm, and barite concrete were irradiated with potential constants of 60kV, 80kV, 110kV, 150kV and gamma radiation of 60 Co. The curves of attenuation and of transmission were obtained for crystal glass, barite plaster and barite concrete (mGy/mA.min) at 1 meter as a function of thickness.Crystal glass has been widely used as shielding material in gamma radiation sources as well as x-ray generating equipment to replace the plumbiferous glass, in order to minimize exposure to individuals. In this work, ten plates of crystal glass, with dimensions of 20cm x 20cm and range of thicknesses from 0.5 to 2.0 cm, and barite concrete were irradiated with potential constants of 60kV, 80kV, 110kV, 150kV and gamma radiation of 60 Co. The curves of attenuation and of transmission were obtained for crystal glass, barite plaster and barite concrete (mGy/mA.min) at 1 meter as a function of thickness. (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.

Potential constants and centrifugal distortion constants of octahedral hexafluoride molecules

Energy Technology Data Exchange (ETDEWEB)

Manivannan, G [Government Thirumagal Mill' s Coll., Gudiyattam, Tamil Nadu (India)

1981-04-01

The kinetic constants method outlined by Thirugnanasambandham (1964) based on Wilson's (1955) group theory has been adapted in evaluating the potential constants for SF/sub 6/, SeF/sub 6/, WF/sub 6/, IrF/sub 6/, UF/sub 6/, NpF/sub 6/, and PuF/sub 6/ using the experimentally observed vibrational frequency data. These constants are used to calculate the centrifugal distortion constants for the first time.

Towards quantifying the role of exact exchange in the prediction hydrogen bond spin-spin coupling constants involving fluorine

Energy Technology Data Exchange (ETDEWEB)

San Fabián, J.; Omar, S.; García de la Vega, J. M., E-mail: garcia.delavega@uam.es [Departamento de Química Física Aplicada, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid (Spain)

2016-08-28

The effect of a fraction of Hartree-Fock exchange on the calculated spin-spin coupling constants involving fluorine through a hydrogen bond is analyzed in detail. Coupling constants calculated using wavefunction methods are revisited in order to get high-level calculations using the same basis set. Accurate MCSCF results are obtained using an additive approach. These constants and their contributions are used as a reference for density functional calculations. Within the density functional theory, the Hartree-Fock exchange functional is split in short- and long-range using a modified version of the Coulomb-attenuating method with the SLYP functional as well as with the original B3LYP. Results support the difficulties for calculating hydrogen bond coupling constants using density functional methods when fluorine nuclei are involved. Coupling constants are very sensitive to the Hartree-Fock exchange and it seems that, contrary to other properties, it is important to include this exchange for short-range interactions. Best functionals are tested in two different groups of complexes: those related with anionic clusters of type [F(HF){sub n}]{sup −} and those formed by difluoroacetylene and either one or two hydrogen fluoride molecules.

Noncognitive Variables to Predict Academic Success among Junior Year Baccalaureate Nursing Students

Science.gov (United States)

Smith, Ellen M. T.

2017-01-01

An equitable predictor of academic success is needed as nursing education strives toward comprehensive preparation of diverse nursing students. The purpose of this study was to discover how Sedlacek's (2004a) Noncognitive Questionnaire (NCQ) and Duckworth & Quinn's (2009) Grit-S predicted baccalaureate nursing student academic performance and…

Are fundamental constants really constant

International Nuclear Information System (INIS)

Norman, E.B.

1986-01-01

Reasons for suspecting that fundamental constants might change with time are reviewed. Possible consequences of such variations are examined. The present status of experimental tests of these ideas is discussed

Generation of constant-amplitude radio-frequency sweeps at a tunnel junction for spin resonance STM

International Nuclear Information System (INIS)

Paul, William; Lutz, Christopher P.; Heinrich, Andreas J.; Baumann, Susanne

2016-01-01

We describe the measurement and successful compensation of the radio-frequency transfer function of a scanning tunneling microscope over a wide frequency range (15.5–35.5 GHz) and with high dynamic range (>50 dB). The precise compensation of cabling resonances and attenuations is critical for the production of constant-voltage frequency sweeps for electric-field driven electron spin resonance (ESR) experiments. We also demonstrate that a well-calibrated tunnel junction voltage is necessary to avoid spurious ESR peaks that can arise due to a non-flat transfer function.

Generation of constant-amplitude radio-frequency sweeps at a tunnel junction for spin resonance STM

Energy Technology Data Exchange (ETDEWEB)

Paul, William; Lutz, Christopher P.; Heinrich, Andreas J. [IBM Research Division, Almaden Research Center, 650 Harry Road, San Jose, California 95120 (United States); Baumann, Susanne [IBM Research Division, Almaden Research Center, 650 Harry Road, San Jose, California 95120 (United States); Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)

2016-07-15

We describe the measurement and successful compensation of the radio-frequency transfer function of a scanning tunneling microscope over a wide frequency range (15.5–35.5 GHz) and with high dynamic range (>50 dB). The precise compensation of cabling resonances and attenuations is critical for the production of constant-voltage frequency sweeps for electric-field driven electron spin resonance (ESR) experiments. We also demonstrate that a well-calibrated tunnel junction voltage is necessary to avoid spurious ESR peaks that can arise due to a non-flat transfer function.

Sensorimotor modulation differs with load type during constant finger force or position.

Directory of Open Access Journals (Sweden)

Hikari Kirimoto

Full Text Available During submaximal isometric contraction, there are two different load types: production of a constant force against a rigid restraint (force task, and maintenance of position against a constant load (position task. Previous studies reported that the time to task failure during a fatigue task was twice as long in the force task compared with the position task. Sensory feedback processing may contribute to these differences. The purpose of the current study was to determine the influence of load types during static muscle contraction tasks on the gating effect, i.e., attenuation of somatosensory-evoked potentials (SEPs and the cortical silent period (cSP. Ten healthy subjects contracted their right first dorsal interosseus muscle by abducting their index finger for 90 s, to produce a constant force against a rigid restraint that was 20% of the maximum voluntary contraction (force task, or to maintain a constant position with 10° abduction of the metacarpophalangeal joint against the same load (position task. Somatosensory evoked potentials (SEPs were recorded from C3' by stimulating either the right ulnar or median nerve at the wrist while maintaining contraction. The cortical silent period (cSP was also elicited by transcranial magnetic stimulation. Reduction of the amplitude of the P45 component of SEPs was significantly larger during the position task than during the force task and under control rest conditions when the ulnar nerve, but not the median nerve, was stimulated. The position task had a significantly shorter cSP duration than the force task. These results suggest the need for more proprioceptive information during the position task than the force task. The shorter duration of the cSP during the position task may be attributable to larger amplitude of heteronymous short latency reflexes. Sensorimotor modulations may differ with load type during constant finger force or position tasks.

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)

Estimation of Anaerobic Debromination Rate Constants of PBDE Pathways Using an Anaerobic Dehalogenation Model.

Science.gov (United States)

Karakas, Filiz; Imamoglu, Ipek

2017-04-01

This study aims to estimate anaerobic debromination rate constants (k m ) of PBDE pathways using previously reported laboratory soil data. k m values of pathways are estimated by modifying a previously developed model as Anaerobic Dehalogenation Model. Debromination activities published in the literature in terms of bromine substitutions as well as specific microorganisms and their combinations are used for identification of pathways. The range of estimated k m values is between 0.0003 and 0.0241 d -1 . The median and maximum of k m values are found to be comparable to the few available biologically confirmed rate constants published in the literature. The estimated k m values can be used as input to numerical fate and transport models for a better and more detailed investigation of the fate of individual PBDEs in contaminated sediments. Various remediation scenarios such as monitored natural attenuation or bioremediation with bioaugmentation can be handled in a more quantitative manner with the help of k m estimated in this study.

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.)

Obtaining the mass attenuation coefficient of the wood to a beam of gamma-ray of 241Am

International Nuclear Information System (INIS)

Costa, Vladimir Eliodoro; Rezende, Marcos Antonio de

2009-01-01

Full text: The quality of wood produced in Brazil reforestation has been the subject of many discussions in the Forestry Sector. SeEKXing to produce a rapid growth and wood quality, the Forestry Sector, found in Applied Nuclear Physics, a precise method of determining the density of wood known as ad hoc technique of attenuation of gamma-ray. The radioisotope used in this technique is that it has a picture 241 Am peak of 59.6 keV gamma-ray. This work has the objective of determining the mass attenuation coefficient of wood of the genus Eucalyptus for 241 Am radioisotope. We used 324 samples of wood from six different treatments: a seminal of Eucalyptus grandis; two clones of E. grandis; three clones of the hybrid E. grandis x E. urophylla. The same assay was used for the six treatments. It was determined the basic density of the samples by the method of immersion in water and then the basic density was converted into apparent density in the moisture equilibrium and it was determined the attenuation coefficient of mass. Preliminary results showed that the attenuation coefficient of mass did not vary between treatments, and its average value 0.1822 ± 0.0015. It was to here that the attenuation coefficient of mass in the wood of the genus Eucalyptus in moisture equilibrium can be constant. (author)

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

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

Inflation with a smooth constant-roll to constant-roll era transition

Science.gov (United States)

Odintsov, S. D.; Oikonomou, V. K.

2017-07-01

In this paper, we study canonical scalar field models, with a varying second slow-roll parameter, that allow transitions between constant-roll eras. In the models with two constant-roll eras, it is possible to avoid fine-tunings in the initial conditions of the scalar field. We mainly focus on the stability of the resulting solutions, and we also investigate if these solutions are attractors of the cosmological system. We shall calculate the resulting scalar potential and, by using a numerical approach, we examine the stability and attractor properties of the solutions. As we show, the first constant-roll era is dynamically unstable towards linear perturbations, and the cosmological system is driven by the attractor solution to the final constant-roll era. As we demonstrate, it is possible to have a nearly scale-invariant power spectrum of primordial curvature perturbations in some cases; however, this is strongly model dependent and depends on the rate of the final constant-roll era. Finally, we present, in brief, the essential features of a model that allows oscillations between constant-roll eras.

From the Rydberg constant to the fundamental constants metrology; De la constante de Rydberg a la metrologie des constantes fondamentales

Energy Technology Data Exchange (ETDEWEB)

Nez, F

2005-06-15

This document reviews the theoretical and experimental achievements of the author since the beginning of his scientific career. This document is dedicated to the spectroscopy of hydrogen, deuterium and helium atoms. The first part is divided into 6 sub-sections: 1) the principles of hydrogen spectroscopy, 2) the measurement of the 2S-nS/nD transitions, 3) other optical frequency measurements, 4) our contribution to the determination of the Rydberg constant, 5) our current experiment on the 1S-3S transition, 6) the spectroscopy of the muonic hydrogen. Our experiments have improved the accuracy of the Rydberg Constant by a factor 25 in 15 years and we have achieved the first absolute optical frequency measurement of a transition in hydrogen. The second part is dedicated to the measurement of the fine structure constant and the last part deals with helium spectroscopy and the search for optical references in the near infrared range. (A.C.)

Determination of attenuation properties of massive ceramic bricks cladded with mortars containing barite used as protective barrier for radiodiagnostic rooms

International Nuclear Information System (INIS)

Barros, Frieda S.; Schelin, Hugo R.; Tilly Junior, Joao G.; Costa, Paulo R.; Nersissian, Denise Y.; Pereira, Marco A.G.

2001-01-01

The purpose of this work is to determine the properties of attenuation of the walls built with massive ceramic bricks to be used as protection barriers in environments of Medicine and Dentistry, when submitted to X-ray diagnosis. Massive ceramic bricks are used thoroughly in constructions as a calking element. The properties of attenuation of these materials were obtained starting from the application of the model of Archer to a group of attenuation curves with wide beams generated in the tensions of 70, 80, 100, 120, 140 and 150 kVp. A radiological equipment of constant potential was used in the Laboratory of IEE/USP, two cameras of ionization of 6cm 3 , coupled to two radiation monitors. The results show that for a tension of 100kVp, the thickness of 10cm of wall made with massive ceramic bricks corresponds to 1mm of lead. (author)

Analysis of source spectra, attenuation, and site effects from central and eastern United States earthquakes

International Nuclear Information System (INIS)

Lindley, G.

1998-02-01

This report describes the results from three studies of source spectra, attenuation, and site effects of central and eastern United States earthquakes. In the first study source parameter estimates taken from 27 previous studies were combined to test the assumption that the earthquake stress drop is roughly a constant, independent of earthquake size. 200 estimates of stress drop and seismic moment from eastern North American earthquakes were combined. It was found that the estimated stress drop from the 27 studies increases approximately as the square-root of the seismic moment, from about 3 bars at 10 20 dyne-cm to 690 bars at 10 25 dyne-cm. These results do not support the assumption of a constant stress drop when estimating ground motion parameters from eastern North American earthquakes. In the second study, broadband seismograms recorded by the United States National Seismograph Network and cooperating stations have been analysed to determine Q Lg as a function of frequency in five regions: the northeastern US, southeastern US, central US, northern Basin and Range, and California and western Nevada. In the third study, using spectral analysis, estimates have been made for the anelastic attenuation of four regional phases, and estimates have been made for the source parameters of 27 earthquakes, including the M b 5.6, 14 April, 1995, West Texas earthquake

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

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.

Attenuation of nuclear orientation of .sup.127./sup.In in GD and the InGDKorringa spin-lattice relaxation time constant

Czech Academy of Sciences Publication Activity Database

Stone, J.; Ohya, S.; Rikovska, J.; Woehr, A.; Betts, P.; Dupák, Jan; Fogelberg, B.; Jacobsson, L.

č. 133 (2001), s. 111 - 115 ISSN 0304-3843 Institutional research plan: CEZ:AV0Z2065902 Keywords : nuclear orientation * Korringa constant Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.634, year: 2001

Ion exchange equilibrium constants

CERN Document Server

Marcus, Y

2013-01-01

Ion Exchange Equilibrium Constants focuses on the test-compilation of equilibrium constants for ion exchange reactions. The book first underscores the scope of the compilation, equilibrium constants, symbols used, and arrangement of the table. The manuscript then presents the table of equilibrium constants, including polystyrene sulfonate cation exchanger, polyacrylate cation exchanger, polymethacrylate cation exchanger, polysterene phosphate cation exchanger, and zirconium phosphate cation exchanger. The text highlights zirconium oxide anion exchanger, zeolite type 13Y cation exchanger, and

Statistical orientation fluctuations: constant angular momentum versus constant rotational frequency constraints

Energy Technology Data Exchange (ETDEWEB)

Goodman, A L [Tulane Univ., New Orleans, LA (United States)

1992-08-01

Statistical orientation fluctuations are calculated with two alternative assumptions: the rotational frequency remains constant as the shape orientation fluctuates; and, the average angular momentum remains constant as the shape orientation fluctuates. (author). 2 refs., 3 figs.

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)

Determination of attenuation factors for mortar of barite in terms of environmental dose equivalent and effective dose

International Nuclear Information System (INIS)

Almeida Junior, Airton T.; Campos, L.L.R.; Araujo, F.G.S.; Santos, M.A.P.; Nogueira, M.S.

2014-01-01

This work addresses the characterization of barite mortars used as Xray shielding materials through the following quantities: mass attenuation coefficient, air kerma, effective dose and ambient dose - H⁎(10). The experiment was carried out with the use of the following reference qualities: RQR4, RQR6, RQR9 e RQR10, specified in accordance with norm IEC 61267: Medical diagnostic Xray equipment - radiation conditions for use in the determination of characteristics. In this study values was determined experimentally for the attenuation of the Cream barite (density 2.99g/cm 3 , collected in the state of Sao Paulo), Purple barite (density 2.95g/cm 3 , collected in the state of Bahia) and White barite (density 3.10g/cm 3 , collected in the state of Paraiba). These materials, in the form of mortar, were disposed in the form of squares namely poof bodies, whose dimensions were 10 x 10 cm and thickness ranging from 3 to 15 mm approximately. In the experimental procedure, these proof bodies were irradiated with a Pantak, model HF320 industrial X-ray apparatus. The potentials applied to the respective X-ray tube were: 60kV, 80kV, 120kV and 150kV at a constant current of 1mA. The attenuation responses in function of thickness, for each of the materials analyzed, were used to draw the attenuation and transmission curves. The efficiency of the barite studied concerning the capacity to attenuate X-ray radiation for X-ray beams ranging from 60 to 150 kV indicated

THE WYOMING SURVEY FOR Hα. III. A MULTI-WAVELENGTH LOOK AT ATTENUATION BY DUST IN GALAXIES OUT TO z ∼ 0.4

International Nuclear Information System (INIS)

Moore, Carolynn A.; Dale, Daniel A.; Barlow, Rebecca J.; Cohen, Seth A.; Cook, David O.; Johnson, L. C.; Kattner, ShiAnne M.; Staudaher, Shawn M.; Lee, Janice C.

2010-01-01

We report results from the Wyoming Survey for Hα (WySH), a comprehensive four-square degree survey to probe the evolution of star-forming galaxies over the latter half of the age of the universe. We have supplemented the Hα data from WySH with infrared data from the Spitzer Wide-area Infrared Extragalactic Survey and ultraviolet data from the Galaxy Evolution Explorer Deep Imaging Survey. This data set provides a multi-wavelength look at the evolution of the attenuation by dust, and here we compare a traditional measure of dust attenuation (L(TIR)/L(FUV)) to a diagnostic based on a recently developed robust star formation rate (SFR) indicator, [Ha obs +24μm]/Ha obs . With such data over multiple epochs, the evolution in the attenuation by dust with redshift can be assessed. We present results from the ELAIS-N1 and Lockman Hole regions at z ∼ 0.16, 0.24, 0.32, and 0.40. While the ensemble averages of both diagnostics are relatively constant from epoch to epoch, each epoch individually exhibits a larger attenuation by dust for higher SFRs. Hence, an epoch-to-epoch comparison at a fixed SFR suggests a mild decrease in dust attenuation with redshift.

Anisotropic constant-roll inflation

Energy Technology Data Exchange (ETDEWEB)

Ito, Asuka; Soda, Jiro [Kobe University, Department of Physics, Kobe (Japan)

2018-01-15

We study constant-roll inflation in the presence of a gauge field coupled to an inflaton. By imposing the constant anisotropy condition, we find new exact anisotropic constant-roll inflationary solutions which include anisotropic power-law inflation as a special case. We also numerically show that the new anisotropic solutions are attractors in the phase space. (orig.)

Mimicking the cosmological constant: Constant curvature spherical solutions in a nonminimally coupled model

International Nuclear Information System (INIS)

Bertolami, Orfeu; Paramos, Jorge

2011-01-01

The purpose of this study is to describe a perfect fluid matter distribution that leads to a constant curvature region, thanks to the effect of a nonminimal coupling. This distribution exhibits a density profile within the range found in the interstellar medium and an adequate matching of the metric components at its boundary. By identifying this constant curvature with the value of the cosmological constant and superimposing the spherical distributions arising from different matter sources throughout the universe, one is able to mimic a large-scale homogeneous cosmological constant solution.

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.

Measured attenuation correction methods

International Nuclear Information System (INIS)

Ostertag, H.; Kuebler, W.K.; Doll, J.; Lorenz, W.J.

1989-01-01

Accurate attenuation correction is a prerequisite for the determination of exact local radioactivity concentrations in positron emission tomography. Attenuation correction factors range from 4-5 in brain studies to 50-100 in whole body measurements. This report gives an overview of the different methods of determining the attenuation correction factors by transmission measurements using an external positron emitting source. The long-lived generator nuclide 68 Ge/ 68 Ga is commonly used for this purpose. The additional patient dose from the transmission source is usually a small fraction of the dose due to the subsequent emission measurement. Ring-shaped transmission sources as well as rotating point or line sources are employed in modern positron tomographs. By masking a rotating line or point source, random and scattered events in the transmission scans can be effectively suppressed. The problems of measured attenuation correction are discussed: Transmission/emission mismatch, random and scattered event contamination, counting statistics, transmission/emission scatter compensation, transmission scan after administration of activity to the patient. By using a double masking technique simultaneous emission and transmission scans become feasible. (orig.)

Molecular equilibrium structures from experimental rotational constants and calculated vibration-rotation interaction constants

DEFF Research Database (Denmark)

Pawlowski, F; Jorgensen, P; Olsen, Jeppe

2002-01-01

A detailed study is carried out of the accuracy of molecular equilibrium geometries obtained from least-squares fits involving experimental rotational constants B(0) and sums of ab initio vibration-rotation interaction constants alpha(r)(B). The vibration-rotation interaction constants have been...... calculated for 18 single-configuration dominated molecules containing hydrogen and first-row atoms at various standard levels of ab initio theory. Comparisons with the experimental data and tests for the internal consistency of the calculations show that the equilibrium structures generated using Hartree......-Fock vibration-rotation interaction constants have an accuracy similar to that obtained by a direct minimization of the CCSD(T) energy. The most accurate vibration-rotation interaction constants are those calculated at the CCSD(T)/cc-pVQZ level. The equilibrium bond distances determined from these interaction...

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)

Stabilized power constant alimentation; Alimentation regulee a puissance constante

Energy Technology Data Exchange (ETDEWEB)

Roussel, L [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1968-06-01

The study and realization of a stabilized power alimentation variable from 5 to 100 watts are described. In order to realize a constant power drift of Lithium compensated diodes, we have searched a 1 per cent precision of regulation and a response time minus than 1 sec. Recent components like Hall multiplicator and integrated amplifiers give this possibility and it is easy to use permutable circuits. (author) [French] On decrit l'etude et la realisation d'une alimentation a puissance constante reglable dans une gamme de 5 a 100 watts. Prevue pour le drift a puissance constante des diodes compensees au lithium, l'etude a ete menee en vue d'obtenir une precision de regulation de 1 pour cent et un temps de reponse inferieur a la seconde. Des systemes recents tels que multiplicateurs a effet Hall et circuits integres ont permis d'atteindre ce but tout en facilitant l'emploi de modules interchangeables. (auteur)

Stabilized power constant alimentation; Alimentation regulee a puissance constante

Energy Technology Data Exchange (ETDEWEB)

Roussel, L. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1968-06-01

The study and realization of a stabilized power alimentation variable from 5 to 100 watts are described. In order to realize a constant power drift of Lithium compensated diodes, we have searched a 1 per cent precision of regulation and a response time minus than 1 sec. Recent components like Hall multiplicator and integrated amplifiers give this possibility and it is easy to use permutable circuits. (author) [French] On decrit l'etude et la realisation d'une alimentation a puissance constante reglable dans une gamme de 5 a 100 watts. Prevue pour le drift a puissance constante des diodes compensees au lithium, l'etude a ete menee en vue d'obtenir une precision de regulation de 1 pour cent et un temps de reponse inferieur a la seconde. Des systemes recents tels que multiplicateurs a effet Hall et circuits integres ont permis d'atteindre ce but tout en facilitant l'emploi de modules interchangeables. (auteur)

From the Rydberg constant to the fundamental constants metrology

International Nuclear Information System (INIS)

Nez, F.

2005-06-01

This document reviews the theoretical and experimental achievements of the author since the beginning of his scientific career. This document is dedicated to the spectroscopy of hydrogen, deuterium and helium atoms. The first part is divided into 6 sub-sections: 1) the principles of hydrogen spectroscopy, 2) the measurement of the 2S-nS/nD transitions, 3) other optical frequency measurements, 4) our contribution to the determination of the Rydberg constant, 5) our current experiment on the 1S-3S transition, 6) the spectroscopy of the muonic hydrogen. Our experiments have improved the accuracy of the Rydberg Constant by a factor 25 in 15 years and we have achieved the first absolute optical frequency measurement of a transition in hydrogen. The second part is dedicated to the measurement of the fine structure constant and the last part deals with helium spectroscopy and the search for optical references in the near infrared range. (A.C.)

Nitrate decreases xanthine oxidoreductase-mediated nitrite reductase activity and attenuates vascular and blood pressure responses to nitrite.

Science.gov (United States)

Damacena-Angelis, Célio; Oliveira-Paula, Gustavo H; Pinheiro, Lucas C; Crevelin, Eduardo J; Portella, Rafael L; Moraes, Luiz Alberto B; Tanus-Santos, Jose E

2017-08-01

Michaelis constant. Together, our results show that nitrate inhibits XOR-mediated NO production from nitrite, and this mechanism may explain how nitrate attenuates the vascular and blood pressure responses to nitrite. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

CONSTANT LEVERAGE AND CONSTANT COST OF CAPITAL: A COMMON KNOWLEDGE HALF-TRUTH

Directory of Open Access Journals (Sweden)

IGNACIO VÉLEZ-PAREJA

2008-01-01

Full Text Available Un enfoque típico para valorar flujos de caja finitos es suponer que el endeudamiento es constante (generalmente como un endeudamiento objetivo o deseado y que por tanto, el costo del patrimonio, Ke y el costo promedio ponderado de capital CPPC, también son constantes. Para los flujos de caja perpetuos, y con el costo de la deuda, Kd como la tasa de descuento para el ahorro en impuestos o escudo fiscal, Ke y el CPPC aplicado al flujo de caja libre FCL son constantes si el endeudamiento es constante. Sin embargo esto no es verdad para los flujos de caja finitos. En este documento mostramos que para flujos de caja finitos, Ke y por lo tanto el CPPC dependen de la tasa de descuento que se utiliza para valorar el ahorro en impuestos, AI y según lo esperado, Ke y el CPPC no son constantes con Kd como la tasa de descuento para el ahorro en impuestos, aunque el endeudamiento sea constante. Ilustramos esta situación con un ejemplo simple. Analizamos cinco métodos: el flujo de caja descontado, FCD, usando APV, el FCD y la formulación tradicional y general del CPPC, el valor presente del flujo de caja del accionista, FCA más deuda y el flujo de caja de capital, FCC.

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.

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...

Constants and thermodynamics of the acid-base equilibria of triglycine in water-ethanol solutions containing sodium perchlorate at 298 K

Science.gov (United States)

Pham Tkhi, L.; Usacheva, T. R.; Tukumova, N. V.; Koryshev, N. E.; Khrenova, T. M.; Sharnin, V. A.

2016-02-01

The acid-base equilibrium constants for glycyl-glycyl-glycine (triglycine) in water-ethanol solvents containing 0.0, 0.1, 0.3, and 0.5 mole fractions of ethanol are determined by potentiometric titration at 298.15 K and an ionic strength of 0.1, maintained with sodium perchlorate. It is established that an increase in the ethanol content in the solvent reduces the dissociation constant of the carboxyl group of triglycine (increases p K 1) and increases the dissociation constant of the amino group of triglycine (decreases p K 2). It is noted that the weakening of the acidic properties of a triglycinium ion upon an increase of the ethanol content in the solvent is due to the attenuation of the solvation shell of the zwitterionic form of triglycine, and to the increased solvation of triglycinium ions. It is concluded that the acid strength of triglycine increases along with a rise in the EtOH content in the solvent, due to the desolvation of the tripeptide zwitterion and the enhanced solvation of protons.

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.

Learning Read-constant Polynomials of Constant Degree modulo Composites

DEFF Research Database (Denmark)

Chattopadhyay, Arkadev; Gavaldá, Richard; Hansen, Kristoffer Arnsfelt

2011-01-01

Boolean functions that have constant degree polynomial representation over a fixed finite ring form a natural and strict subclass of the complexity class \\textACC0ACC0. They are also precisely the functions computable efficiently by programs over fixed and finite nilpotent groups. This class...... is not known to be learnable in any reasonable learning model. In this paper, we provide a deterministic polynomial time algorithm for learning Boolean functions represented by polynomials of constant degree over arbitrary finite rings from membership queries, with the additional constraint that each variable...

Natural Attenuation of Arsenic, Cadmium, Lead, and Zinc Using Hydrograph Separation

Science.gov (United States)

Burrows, J. E.; Peters, S. C.

2009-12-01

Strategies for remediating contaminated sites range from complete removal of the contaminated soil to in-situ monitored natural attenuation. The decision to let a property naturally attenuate is partially based on the estimated time it will take to return to ambient conditions. The Lehigh Gap Wildlife Refuge at Palmerton, PA was historically contaminated with arsenic, cadmium, lead, and zinc from a zinc smelting operation that ceased emissions twenty-nine years ago. This property provides an opportunity to assess whether the length of time required for the natural attenuation of metals in soil has been achieved using a watershed mass balance approach, focusing particularly on perturbations observed in the concentration-discharge relationships of contaminants compared to the conservative tracers sodium and chloride, and silicon as an indicator of rock-water interactions. Water samples were collected from 3 springs in the Wildlife Refuge for approximately 4 days following the onset of storm events and analyzed for cation and anion concentrations. Preliminary results show that while the concentrations of arsenic and lead were below detection limits, the fluxes of zinc and cadmium increase corresponding with the peak in the hydrograph relative to the fluxes of the tracers, indicating the solutes are being released from adsorption sites located in an unsaturated zone that is temporarily inundated during storm events. In comparison, the flux of the tracers remains constant, indicative of a steady-state leakage of the solutes from their respective reservoirs in the soil. Along with flux, the concentrations of zinc and cadmium also increase following the rise in discharge after storm events, further suggesting that these contaminants are being mobilized out of the soil profile.

CT attenuation in normal aging and Alzheimer's disease

International Nuclear Information System (INIS)

Kim, W.S.; Pearlson, G.D.; Goldfinger, A.D.; Tune, L.E.; Heyler, G.

1986-01-01

113 screened normal volunteers aged 18-85 and 50 elderly demented individuals meeting NINCDS/ADRDA criteria for probable senile dementia of the Alzheimer type, (SDAT), received a non-contrast x-CT head scan on a single 512x512 matrix Siemens Somatom DR3 Scanner. Scanning parameters (KV,MA) were kept constant, and the authors used a specially designed head holder to ensure a uniform scanning angle. Standard 8mm thick cuts, at zero degrees to the supra-orbito-meatal line, were taken through the entire brain. A ''phantom'' consisting of plastics of several different attenuation values was scanned before each patient as a reference to correct for any numerical drift in the scanner. Both patients and controls were scanned during the same sessions to eliminate possible systematic bias, and a single CT technologist carried out all scanning. Numerical CT data were collected on magnetic tape for analysis on a specially designed image processing system. Software was used to read CT density data from the 512x512 matrix scanner output tapes and to transfer the resulting image in standardized format to hard disk on the processing system. This system consists of a PDP-11-34 computer, linked to a Gould DeAnza IP-5000 image processors, hard disk system and tape drive. Once transferred to disk, images were rated blindly to subject identity or diagnosis by another 2 separate raters using a computer-linked cursor, and digitizer tablet. These numerical attenuation data from various anatomically defined regions of interest, (ROI's), were then corrected for head size using a regression model

Constant leverage and constant cost of capital : A common knowledge half-truth

OpenAIRE

Vélez Pareja, Ignacio; Ibragimov, Rauf; Tham , Joseph

2008-01-01

Un enfoque típico para valorar flujos de caja finitos es suponer que el endeudamiento es constante (generalmente como un endeudamiento objetivo o deseado) y que por tanto, el costo del patrimonio, Ke y el costo promedio ponderado de capital CPPC, también son constantes. Para los flujos de caja perpetuos, y con el costo de la deuda, Kd como la tasa de descuento para el ahorro en impuestos o escudo fiscal, Ke y el CPPC aplicado al flujo de caja libre FCL son constantes si el endeudamiento es co...

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

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...

FORMATION CONSTANTS AND THERMODYNAMIC ...

African Journals Online (AJOL)

KEY WORDS: Metal complexes, Schiff base ligand, Formation constant, DFT calculation ... best values for the formation constants of the proposed equilibrium model by .... to its positive charge distribution and the ligand deformation geometry.

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

Association constants of telluronium salts

International Nuclear Information System (INIS)

Kovach, N.A.; Rivkin, B.B.; Sadekov, T.D.; Shvajka, O.P.

1996-01-01

Association constants in acetonitrile of triphenyl telluronium salts, which are dilute electrolytes, are determined through the conductometry method. Satisfactory correlation dependence of constants of interion association and threshold molar electroconductivity on the Litvinenko-Popov constants for depositing groups is identified. 6 refs

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)

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...

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.

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

MR-based attenuation correction for PET/MRI neurological studies with continuous-valued attenuation coefficients for bone through a conversion from R2* to CT-Hounsfield units.

Science.gov (United States)

Juttukonda, Meher R; Mersereau, Bryant G; Chen, Yasheng; Su, Yi; Rubin, Brian G; Benzinger, Tammie L S; Lalush, David S; An, Hongyu

2015-05-15

MR-based correction for photon attenuation in PET/MRI remains challenging, particularly for neurological applications requiring quantitation of data. Existing methods are either not sufficiently accurate or are limited by the computation time required. The goal of this study was to develop an MR-based attenuation correction method that accurately separates bone tissue from air and provides continuous-valued attenuation coefficients for bone. PET/MRI and CT datasets were obtained from 98 subjects (mean age [±SD]: 66yrs [±9.8], 57 females) using an IRB-approved protocol and with informed consent. Subjects were injected with 352±29MBq of (18)F-Florbetapir tracer, and PET acquisitions were begun either immediately or 50min after injection. CT images of the head were acquired separately using a PET/CT system. Dual echo ultrashort echo-time (UTE) images and two-point Dixon images were acquired. Regions of air were segmented via a threshold of the voxel-wise multiplicative inverse of the UTE echo 1 image. Regions of bone were segmented via a threshold of the R2* image computed from the UTE echo 1 and UTE echo 2 images. Regions of fat and soft tissue were segmented using fat and water images decomposed from the Dixon images. Air, fat, and soft tissue were assigned linear attenuation coefficients (LACs) of 0, 0.092, and 0.1cm(-1), respectively. LACs for bone were derived from a regression analysis between corresponding R2* and CT values. PET images were reconstructed using the gold standard CT method and the proposed CAR-RiDR method. The RiDR segmentation method produces mean Dice coefficient±SD across subjects of 0.75±0.05 for bone and 0.60±0.08 for air. The CAR model for bone LACs greatly improves accuracy in estimating CT values (28.2%±3.0 mean error) compared to the use of a constant CT value (46.9%±5.8, punits. From our analysis, we conclude that the proposed method closely approaches (<3% error) the gold standard CT-scaled method in PET reconstruction accuracy

An Estimation of Wave Attenuation Factor in Ultrasonic Assisted Gravity Drainage Process

Directory of Open Access Journals (Sweden)

Behnam Keshavarzi

2014-01-01

Full Text Available It has been proved that ultrasonic energy can considerably increase the amount of oil recovery in an immiscible displacement process. Although many studies have been performed on investigating the roles of ultrasonic waves, based on the best of our knowledge, little attention has been paid to evaluate wave attenuation parameter, which is an important parameter in the determination of the energy delivered to the porous medium. In this study, free fall gravity drainage process is investigated in a glass bead porous medium. Kerosene and Dorud crude oil are used as the wetting phases and air is used as the non-wetting phase. A piston-like displacement model with considering constant capillary pressure and applying Corey type approximation for relative permeabilities of both wetting and nonwetting phases is applied. A pressure term is considered to describe the presence of ultrasonic waves and the attenuation factor of ultrasonic waves is calculated by evaluating the value of external pressure applied to enhance the flow using the history matching of the data in the presence and absence of ultrasonic waves. The results introduce the attenuation factor as an important parameter in the process of ultrasonic assisted gravity drainage. The results show that only a low percentage of the ultrasonic energy (5.8% for Dorud crude oil and 3.3% for kerosene is delivered to the flow of the fluid; however, a high increase in oil recovery enhancement (15% for Dorud crude oil and 12% for Kerosene is observed in the experiments. This proves that the ultrasonic waves, even when the contribution is not substantial, can be a significantly efficient method for flow enhancement.

Short-term prediction of rain attenuation level and volatility in Earth-to-Satellite links at EHF band

Directory of Open Access Journals (Sweden)

L. de Montera

2008-08-01

Full Text Available This paper shows how nonlinear models originally developed in the finance field can be used to predict rain attenuation level and volatility in Earth-to-Satellite links operating at the Extremely High Frequencies band (EHF, 20–50 GHz. A common approach to solving this problem is to consider that the prediction error corresponds only to scintillations, whose variance is assumed to be constant. Nevertheless, this assumption does not seem to be realistic because of the heteroscedasticity of error time series: the variance of the prediction error is found to be time-varying and has to be modeled. Since rain attenuation time series behave similarly to certain stocks or foreign exchange rates, a switching ARIMA/GARCH model was implemented. The originality of this model is that not only the attenuation level, but also the error conditional distribution are predicted. It allows an accurate upper-bound of the future attenuation to be estimated in real time that minimizes the cost of Fade Mitigation Techniques (FMT and therefore enables the communication system to reach a high percentage of availability. The performance of the switching ARIMA/GARCH model was estimated using a measurement database of the Olympus satellite 20/30 GHz beacons and this model is shown to outperform significantly other existing models.

The model also includes frequency scaling from the downlink frequency to the uplink frequency. The attenuation effects (gases, clouds and rain are first separated with a neural network and then scaled using specific scaling factors. As to the resulting uplink prediction error, the error contribution of the frequency scaling step is shown to be larger than that of the downlink prediction, indicating that further study should focus on improving the accuracy of the scaling factor.

Short-term prediction of rain attenuation level and volatility in Earth-to-Satellite links at EHF band

Science.gov (United States)

de Montera, L.; Mallet, C.; Barthès, L.; Golé, P.

2008-08-01

This paper shows how nonlinear models originally developed in the finance field can be used to predict rain attenuation level and volatility in Earth-to-Satellite links operating at the Extremely High Frequencies band (EHF, 20 50 GHz). A common approach to solving this problem is to consider that the prediction error corresponds only to scintillations, whose variance is assumed to be constant. Nevertheless, this assumption does not seem to be realistic because of the heteroscedasticity of error time series: the variance of the prediction error is found to be time-varying and has to be modeled. Since rain attenuation time series behave similarly to certain stocks or foreign exchange rates, a switching ARIMA/GARCH model was implemented. The originality of this model is that not only the attenuation level, but also the error conditional distribution are predicted. It allows an accurate upper-bound of the future attenuation to be estimated in real time that minimizes the cost of Fade Mitigation Techniques (FMT) and therefore enables the communication system to reach a high percentage of availability. The performance of the switching ARIMA/GARCH model was estimated using a measurement database of the Olympus satellite 20/30 GHz beacons and this model is shown to outperform significantly other existing models. The model also includes frequency scaling from the downlink frequency to the uplink frequency. The attenuation effects (gases, clouds and rain) are first separated with a neural network and then scaled using specific scaling factors. As to the resulting uplink prediction error, the error contribution of the frequency scaling step is shown to be larger than that of the downlink prediction, indicating that further study should focus on improving the accuracy of the scaling factor.

Quintessence and the cosmological constant

International Nuclear Information System (INIS)

Doran, M.; Wetterich, C.

2003-01-01

Quintessence -- the energy density of a slowly evolving scalar field -- may constitute a dynamical form of the homogeneous dark energy in the universe. We review the basic idea in the light of the cosmological constant problem. Cosmological observations or a time variation of fundamental 'constants' can distinguish quintessence from a cosmological constant

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).

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)

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.

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.

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.)

Analysis of biological samples by x-ray attenuation measurements

International Nuclear Information System (INIS)

Cesareo, R.

1988-01-01

Over the last few years there has been an increasing interest in X-ray attenuation measurements, mainly due to the enormous development of computer assisted tomography (CAT). With CAT, analytical information concerning the density and the mean atomic number distributions in a sample is deduced from a large number of attenuation measurements. Particular transmission methods developed, based on the differential attenuation method are discussed. The theoretical background for attenuation of radiation and for differential attenuation of radiation is given. Details about the generation of monoenergetic X-rays are discussed. Applications of attenuation measurements in the field of Medicine are presented

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

Cosmological constants and variations

International Nuclear Information System (INIS)

Barrow, John D

2005-01-01

We review properties of theories for the variation of the gravitation and fine structure 'constants'. We highlight some general features of the cosmological models that exist in these theories with reference to recent quasar data that is consistent with time-variation in the fine structure 'constant' since a redshift of 3.5. The behaviour of a simple class of varying alpha cosmologies is outlined in the light of all the observational constraints. We also discuss some of the consequences of varying 'constants' for oscillating universes and show by means of exact solutions that they appear to evolve monotonically in time even though the scale factor of the universe oscillates

The Fine Structure Constant

Indian Academy of Sciences (India)

IAS Admin

The article discusses the importance of the fine structure constant in quantum mechanics, along with the brief history of how it emerged. Al- though Sommerfelds idea of elliptical orbits has been replaced by wave mechanics, the fine struc- ture constant he introduced has remained as an important parameter in the field of ...

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

Tachyon constant-roll inflation

Science.gov (United States)

Mohammadi, A.; Saaidi, Kh.; Golanbari, T.

2018-04-01

The constant-roll inflation is studied where the inflaton is taken as a tachyon field. Based on this approach, the second slow-roll parameter is taken as a constant which leads to a differential equation for the Hubble parameter. Finding an exact solution for the Hubble parameter is difficult and leads us to a numerical solution for the Hubble parameter. On the other hand, since in this formalism the slow-roll parameter η is constant and could not be assumed to be necessarily small, the perturbation parameters should be reconsidered again which, in turn, results in new terms appearing in the amplitude of scalar perturbations and the scalar spectral index. Utilizing the numerical solution for the Hubble parameter, we estimate the perturbation parameter at the horizon exit time and compare it with observational data. The results show that, for specific values of the constant parameter η , we could have an almost scale-invariant amplitude of scalar perturbations. Finally, the attractor behavior for the solution of the model is presented, and we determine that the feature could be properly satisfied.

Elastic wave attenuation in rocks containing fluids

International Nuclear Information System (INIS)

Berryman, J.G.

1986-01-01

The low-frequency limit of Biot's theory of fluid-saturated porous media predicts that the coefficients for viscous attenuation of shear waves and of the fast compressional wave are proportional to the fluid permeability. Although the observed attenuation is generally in qualitative agreement with the theory, the magnitude of the observed attenuation coefficient in rocks is often more than an order of magnitude higher than expected. This apparent dilemma can be resolved without invoking other attenuation mechanisms if the intrinsic permeability of the rock is inhomogeneous and varies widely in magnitude. A simple calculation of the overall behavior of a layered porous material using local-flow Biot theory shows that the effective permeability for attenuation is the mean of the constituent permeabilities while the effective permeability for fluid flow is the harmonic mean. When the range of variation in the local permeability is one or more orders of magnitude, this difference in averaging method can easily explain some of the observed discrepancies

Estimating Rain Attenuation In Satellite Communication Links

Science.gov (United States)

Manning, R. M.

1991-01-01

Attenuation computed with help of statistical model and meteorological data. NASA Lewis Research Center Satellite Link Attenuation Model (SLAM) program QuickBASIC computer program evaluating static and dynamic statistical assessment of impact of rain attenuation on communication link established between Earth terminal and geosynchronous satellite. Application in specification, design, and assessment of satellite communication links for any terminal location in continental United States. Written in Microsoft QuickBASIC.

An acoustic eikonal equation for attenuating orthorhombic media

KAUST Repository

Hao, Qi

2017-04-06

Attenuating orthorhombic models are often used to describe the azimuthal variation of the seismic wave velocity and amplitude in finely layered hydrocarbon reservoirs with vertical fractures. In addition to the P-wave related medium parameters, shear wave parameters are also present in the complex eikonal equation needed to describe the P-wave complex-valued traveltime in an attenuating orthorhombic medium, which increases the complexity of using the P-wave traveltime to invert for the medium parameters in practice. Here, we use the acoustic assumption to derive an acoustic eikonal equation that approximately governs the complex-valued traveltime of P-waves in an attenuating orthorhombic medium. For a homogeneous attenuating orthorhombic media, we solve the eikonal equation using a combination of the perturbation method and Shanks transform. For a horizontal attenuating orthorhombic layer, both the real and imaginary part of the complex-valued reflection traveltime have nonhyperbolic behaviors in terms of the source-receiver offset. Similar to the roles of normal moveout (NMO) velocity and anellipticity, the attenuation NMO velocity and the attenuation anellipticity characterize the variation of the imaginary part of the complex-valued reflection traveltime around zero source-receiver offset.

Varying Constants, Gravitation and Cosmology

Directory of Open Access Journals (Sweden)

Jean-Philippe Uzan

2011-03-01

Full Text Available Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter. This will induce a violation of the universality of free fall. Thus, it is of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, solar system observations, meteorite dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describe the main theoretical frameworks in which the low-energy constants may actually be varying and we focus on the unification mechanisms and the relations between the variation of different constants. To finish, we discuss the more speculative possibility of understanding their numerical values and the apparent fine-tuning that they confront us with.

Nuclear constants

International Nuclear Information System (INIS)

Foos, J.

1999-01-01

This paper is written in two tables. The first one describes the different particles (bosons and fermions). The second one gives the isotopes nuclear constants of the different elements, for Z = 1 to 56. (A.L.B.)

Nuclear constants

International Nuclear Information System (INIS)

Foos, J.

2000-01-01

This paper is written in two tables. The first one describes the different particles (bosons and fermions). The second one gives the isotopes nuclear constants of the different elements, for Z = 56 to 68. (A.L.B.)

Nuclear constants

International Nuclear Information System (INIS)

Foos, J.

1999-01-01

This paper is written in two tables. The first one describes the different particles (bosons and fermions). The second one gives the isotopes nuclear constants of the different elements, for Z = 56 to 68. (A.L.B.)

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

Energy Technology Data Exchange (ETDEWEB)

Yamshchikov, Vladimir, E-mail: yaximik@gmail.com; Manuvakhova, Marina; Rodriguez, Efrain

2016-01-15

Direct attenuation of West Nile (WN) virus strain NY99 for the purpose of vaccine development is not feasible due to its high virulence and pathogenicity. Instead, we created highly attenuated chimeric virus W1806 with the serological identity of NY99. To further attenuate W1806, we investigated effects of mutations found in Japanese encephalitis virus vaccine SA14-14-2. WN viruses carrying all attenuating mutations lost infectivity in mammalian, but not in mosquito cells. No single reversion restored infectivity in mammalian cells, although increased infectivity in mosquito cells was observed. To identify a subset of mutations suitable for further attenuation of W1806, we analyzed effects of E{sub 138}K and K{sub 279}M changes on virulence, growth properties, and immunogenicity of derivatized W956, from which chimeric W1806 inherited its biological properties and attenuation profile. Despite strong dominant attenuating effect, introduction of only two mutations was not sufficient for attenuating W1806 to the safety level acceptable for human use. - Highlights: • Further attenuation of a WN vaccine precursor is outlined. • Effect of SA14-14-2 attenuating mutations is tested. • Mechanism of attenuation is proposed and illustrated. • The need for additional attenuating mutations is justified.

Determination of protonation constants of hydroquinone and stability constants of Th(IV) hydroquinone complex

International Nuclear Information System (INIS)

Sawant, R.M.; Ramakumar, K.L.; Sharma, R.S.

2003-01-01

Protonation constants of hydroquinone and stability constants of thorium hydroquinone complexes were determined in 1 M NaClO 4 medium at 25 ± 0.5 degC, by varying concentration of thorium, using pH titration technique. Protonation constants of hydroquinone (β 1H = [HQ]/[H][Q] and β 2H = [H 2 Q]/[H] 2 [Q]) were found to be β 1H = 11.404 ± 0.014 and β 2H = 21.402 ± 0.012. The analysis of titration data of thorium-hydroquinone system appears to indicate the formation of species Th(H 2 Q) 3 (OH) and Th(H 2 O) 4 (OH). Equilibrium constants obtained for these species are -log β 13-I = 48.51 ± 0.67 and -log β 14-1 64.86 ± 1.25 respectively which are not reported in the literature. (author)

Nuclear constants

International Nuclear Information System (INIS)

Foos, J.

1998-01-01

This paper is made of two tables. The first table describes the different particles (bosons and fermions) while the second one gives the nuclear constants of isotopes from the different elements with Z = 1 to 25. (J.S.)

Connecting Fundamental Constants

International Nuclear Information System (INIS)

Di Mario, D.

2008-01-01

A model for a black hole electron is built from three basic constants only: h, c and G. The result is a description of the electron with its mass and charge. The nature of this black hole seems to fit the properties of the Planck particle and new relationships among basic constants are possible. The time dilation factor in a black hole associated with a variable gravitational field would appear to us as a charge; on the other hand the Planck time is acting as a time gap drastically limiting what we are able to measure and its dimension will appear in some quantities. This is why the Planck time is numerically very close to the gravitational/electric force ratio in an electron: its difference, disregarding a π√(2) factor, is only 0.2%. This is not a coincidence, it is always the same particle and the small difference is between a rotating and a non-rotating particle. The determination of its rotational speed yields accurate numbers for many quantities, including the fine structure constant and the electron magnetic moment

Photostimulated attenuation of hypersound in superlattice

International Nuclear Information System (INIS)

Mensah, S.Y.; Allotey, F.K.; Adjepong, S.K.

1992-10-01

Photostimulated attenuation of hypersound in semiconductor superlattice has been investigated. It is shown that the attenuation coefficient depends on the phonon wave vector q in an oscillatory manner and that from this oscillation the band width Δ of superlattice can be found. (author). 14 refs, 1 fig

Calculation Of Pneumatic Attenuation In Pressure Sensors

Science.gov (United States)

Whitmore, Stephen A.

1991-01-01

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

TRIPOLI 01, a three-dimensional polykinetic Monte Carlo program. Pt.2. Constant data input and results obtained for a complex bench-mark example

International Nuclear Information System (INIS)

Baur, A.; Bourdet, L.; Gonnord, J.; Nimal, J.C.; Vergnaud, T.

1977-01-01

Some properties of the sub-routines included in TRIPOLI for the constant data input are briefly reviewed. The bench-mark example then proposed is a problem of the contour lines of a neutron-opaque shield. The example is derived from activation calculations for the secondary sodium in a fast reactor provided with an integrated shield of Phenix type. The dimensions have been reduced so as the geometry to be simplified, and the constant data load reduced. Besides the rate of 24 Na formation by capture in the exchanger region, the attenuation of various detector responses all along the neutron trajectory was taken into account. The detectors chiefly used were: 103 Rh activation from (n,n') reactions for fast neutron detection, the activation Mn detectors, either bare or under cadmium, for detecting thermal and epithermal neutrons respectively [fr

Constant load and constant displacement stress corrosion in simulated water reactor environments

International Nuclear Information System (INIS)

Lloyd, G.J.

1987-02-01

The stress corrosion behaviour of selected water reactor constructional materials, as determined by constant load or constant displacement test techniques, is reviewed. Experimental results obtained using a very wide range of conditions have been collected in a form for easy reference. A discussion is given of some apparent trends in these data. The possible reasons for these trends are considered together with a discussion of how the observed discrepancies may be resolved. (author)

Study of mass attenuation coefficients and effective atomic numbers of bismuth-ground granulated blast furnace slag concretes

International Nuclear Information System (INIS)

Kumar, Sandeep; Singh, Sukhpal

2016-01-01

Five samples of Bismuth-Ground granulated blast furnace slag (Bi-GGBFS) concretes were prepared using composition (0.6 cement + x Bi_2O_3 + (0.4-x) GGBFS, x = 0.05, 0.10, 0.15, 0.20 and 0.25) by keeping constant water (W) cement (C) ratio. Mass attenuation coefficients (μ_m) of these prepared samples were calculated using a computer program winXCOM at different gamma ray energies, whereas effective atomic numbers (Z_e_f_f) is calculated using mathematical formulas. The radiation shielding properties of Bi-GGBFS concrete has been compared with standard radiation shielding concretes.

Dose reduction using a dynamic, piecewise-linear attenuator

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); Fleischmann, Dominik [Department of Radiology, 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)

2014-02-15

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

Evaluation of various energy windows at different radionuclides for scatter and attenuation correction in nuclear medicine.

Science.gov (United States)

Asgari, Afrouz; Ashoor, Mansour; Sohrabpour, Mostafa; Shokrani, Parvaneh; Rezaei, Ali

2015-05-01

Improving signal to noise ratio (SNR) and qualified images by the various methods is very important for detecting the abnormalities at the body organs. Scatter and attenuation of photons by the organs lead to errors in radiopharmaceutical estimation as well as degradation of images. The choice of suitable energy window and the radionuclide have a key role in nuclear medicine which appearing the lowest scatter fraction as well as having a nearly constant linear attenuation coefficient as a function of phantom thickness. The energy windows of symmetrical window (SW), asymmetric window (ASW), high window (WH) and low window (WL) using Tc-99m and Sm-153 radionuclide with solid water slab phantom (RW3) and Teflon bone phantoms have been compared, and Matlab software and Monte Carlo N-Particle (MCNP4C) code were modified to simulate these methods and obtaining the amounts of FWHM and full width at tenth maximum (FWTM) using line spread functions (LSFs). The experimental data were obtained from the Orbiter Scintron gamma camera. Based on the results of the simulation as well as experimental work, the performance of WH and ASW display of the results, lowest scatter fraction as well as constant linear attenuation coefficient as a function of phantom thickness. WH and ASW were optimal windows in nuclear medicine imaging for Tc-99m in RW3 phantom and Sm-153 in Teflon bone phantom. Attenuation correction was done for WH and ASW optimal windows and for these radionuclides using filtered back projection algorithm. Results of simulation and experimental show that very good agreement between the set of experimental with simulation as well as theoretical values with simulation data were obtained which was nominally less than 7.07 % for Tc-99m and less than 8.00 % for Sm-153. Corrected counts were not affected by the thickness of scattering material. The Simulated results of Line Spread Function (LSF) for Sm-153 and Tc-99m in phantom based on four windows and TEW method were

Seismic attenuation system for a nuclear reactor

Energy Technology Data Exchange (ETDEWEB)

Liszkai, Tamas; Cadell, Seth

2018-01-30

A system for attenuating seismic forces includes a reactor pressure vessel containing nuclear fuel and a containment vessel that houses the reactor pressure vessel. Both the reactor pressure vessel and the containment vessel include a bottom head. Additionally, the system includes a base support to contact a support surface on which the containment vessel is positioned in a substantially vertical orientation. An attenuation device is located between the bottom head of the reactor pressure vessel and the bottom head of the containment vessel. Seismic forces that travel from the base support to the reactor pressure vessel via the containment vessel are attenuated by the attenuation device in a direction that is substantially lateral to the vertical orientation of the containment vessel.

Construction of Lines of Constant Density and Constant Refractive Index for Ternary Liquid Mixtures.

Science.gov (United States)

Tasic, Aleksandar Z.; Djordjevic, Bojan D.

1983-01-01

Demonstrates construction of density constant and refractive index constant lines in triangular coordinate system on basis of systematic experimental determinations of density and refractive index for both homogeneous (single-phase) ternary liquid mixtures (of known composition) and the corresponding binary compositions. Background information,…

Electron Effective-Attenuation-Length Database

Science.gov (United States)

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

RNA structure and scalar coupling constants

Energy Technology Data Exchange (ETDEWEB)

Tinoco, I. Jr.; Cai, Z.; Hines, J.V.; Landry, S.M.; SantaLucia, J. Jr.; Shen, L.X.; Varani, G. [Univ. of California, Berkeley, CA (United States)

1994-12-01

Signs and magnitudes of scalar coupling constants-spin-spin splittings-comprise a very large amount of data that can be used to establish the conformations of RNA molecules. Proton-proton and proton-phosphorus splittings have been used the most, but the availability of {sup 13}C-and {sup 15}N-labeled molecules allow many more coupling constants to be used for determining conformation. We will systematically consider the torsion angles that characterize a nucleotide unit and the coupling constants that depend on the values of these torsion angles. Karplus-type equations have been established relating many three-bond coupling constants to torsion angles. However, one- and two-bond coupling constants can also depend on conformation. Serianni and coworkers measured carbon-proton coupling constants in ribonucleosides and have calculated their values as a function of conformation. The signs of two-bond coupling can be very useful because it is easier to measure a sign than an accurate magnitude.

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

GOODS-HERSCHEL: STAR FORMATION, DUST ATTENUATION, AND THE FIR–RADIO CORRELATION ON THE MAIN SEQUENCE OF STAR-FORMING GALAXIES UP TO z ≃ 4

Energy Technology Data Exchange (ETDEWEB)

Pannella, M.; Elbaz, D.; Daddi, E.; Hwang, H. S.; Schreiber, C.; Strazzullo, V.; Aussel, H.; Bethermin, M.; Cibinel, A.; Juneau, S.; Floc’h, E. Le; Leiton, R. [Laboratoire AIM-Paris-Saclay, CEA/DSM/Irfu—CNRS—Université Paris Diderot, CEA-Saclay, F-91191 Gif-sur-Yvette (France); Dickinson, M. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Buat, V. [Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR7326, F-13388, Marseille (France); Charmandaris, V.; Magdis, G. [Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, 15236, Penteli (Greece); Ivison, R. J. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Borgne, D. Le [Institut d’Astrophysique de Paris, UMR 7095, CNRS, 98bis boulevard Arago, F-75005 Paris (France); Lin, L. [Institute of Astronomy and Astrophysics, Academia Sinica, Taipei 106, Taiwan (China); Morrison, G. E. [Institute for Astronomy, University of Hawaii, Honolulu, Hawaii, HI-96822 (United States); and others

2015-07-10

We use deep panchromatic data sets in the GOODS-N field, from GALEX to the deepest Herschel far-infrared (FIR) and VLA radio continuum imaging, to explore the evolution of star-formation activity and dust attenuation properties of star-forming galaxies to z ≃ 4, using mass-complete samples. Our main results can be summarized as follows: (i) the slope of the star-formation rate–M{sub *} correlation is consistent with being constant ≃0.8 up to z ≃ 1.5, while its normalization keeps increasing with redshift; (ii) for the first time we are able to explore the FIR–radio correlation for a mass-selected sample of star-forming galaxies: the correlation does not evolve up to z ≃ 4; (iii) we confirm that galaxy stellar mass is a robust proxy for UV dust attenuation in star-forming galaxies, with more massive galaxies being more dust attenuated. Strikingly, we find that this attenuation relation evolves very weakly with redshift, with the amount of dust attenuation increasing by less than 0.3 mag over the redshift range [0.5–4] for a fixed stellar mass; (iv) the correlation between dust attenuation and the UV spectral slope evolves with redshift, with the median UV slope becoming bluer with redshift. By z ≃ 3, typical UV slopes are inconsistent, given the measured dust attenuations, with the predictions of commonly used empirical laws. (v) Finally, building on existing results, we show that gas reddening is marginally larger (by a factor of around 1.3) than the stellar reddening at all redshifts probed. Our results support a scenario where the ISM conditions of typical star-forming galaxies evolve with redshift, such that at z ≥ 1.5 Main Sequence galaxies have ISM conditions moving closer to those of local starbursts.

Determination of rate constants and branching ratios for TCE degradation by zero-valent iron using a chain decay multispecies model.

Science.gov (United States)

Hwang, Hyoun-Tae; Jeen, Sung-Wook; Sudicky, Edward A; Illman, Walter A

2015-01-01

The applicability of a newly-developed chain-decay multispecies model (CMM) was validated by obtaining kinetic rate constants and branching ratios along the reaction pathways of trichloroethene (TCE) reduction by zero-valent iron (ZVI) from column experiments. Changes in rate constants and branching ratios for individual reactions for degradation products over time for two columns under different geochemical conditions were examined to provide ranges of those parameters expected over the long-term. As compared to the column receiving deionized water, the column receiving dissolved CaCO3 showed higher mean degradation rates for TCE and all of its degradation products. However, the column experienced faster reactivity loss toward TCE degradation due to precipitation of secondary carbonate minerals, as indicated by a higher value for the ratio of maximum to minimum TCE degradation rate observed over time. From the calculated branching ratios, it was found that TCE and cis-dichloroethene (cis-DCE) were dominantly dechlorinated to chloroacetylene and acetylene, respectively, through reductive elimination for both columns. The CMM model, validated by the column test data in this study, provides a convenient tool to determine simultaneously the critical design parameters for permeable reactive barriers and natural attenuation such as rate constants and branching ratios. Copyright © 2015 Elsevier B.V. All rights reserved.

Stability Constants of Some Biologically Important Pyrazoles and Their Ni2+ Complexes in Different Dielectric Constant of Medium

Directory of Open Access Journals (Sweden)

S. D. Deosarkar

2012-01-01

Full Text Available The proton-ligand stability constants of some biologically important new pyrazoles and formation constants of their complexes with Ni(II were determined at 0.1 mol dm-3 ionic strength and at 303.15 K in different dielectric constant of dioxane-water mixture by potentiometric method. The Calvin-Bjerrum's pH-titration technique as used by Irving and Rossotti was used for determination of stability constants. The results enabled to study the electrostatic forces of attraction between metal ion and ligand with changes in dielectric constant of the medium.

A natural cosmological constant from chameleons

International Nuclear Information System (INIS)

Nastase, Horatiu; Weltman, Amanda

2015-01-01

We present a simple model where the effective cosmological constant appears from chameleon scalar fields. For a Kachru–Kallosh–Linde–Trivedi (KKLT)-inspired form of the potential and a particular chameleon coupling to the local density, patches of approximately constant scalar field potential cluster around regions of matter with density above a certain value, generating the effect of a cosmological constant on large scales. This construction addresses both the cosmological constant problem (why Λ is so small, yet nonzero) and the coincidence problem (why Λ is comparable to the matter density now)

A natural cosmological constant from chameleons

Directory of Open Access Journals (Sweden)

Horatiu Nastase

2015-07-01

Full Text Available We present a simple model where the effective cosmological constant appears from chameleon scalar fields. For a Kachru–Kallosh–Linde–Trivedi (KKLT-inspired form of the potential and a particular chameleon coupling to the local density, patches of approximately constant scalar field potential cluster around regions of matter with density above a certain value, generating the effect of a cosmological constant on large scales. This construction addresses both the cosmological constant problem (why Λ is so small, yet nonzero and the coincidence problem (why Λ is comparable to the matter density now.

A natural cosmological constant from chameleons

Energy Technology Data Exchange (ETDEWEB)

Nastase, Horatiu, E-mail: nastase@ift.unesp.br [Instituto de Física Teórica, UNESP-Universidade Estadual Paulista, R. Dr. Bento T. Ferraz 271, Bl. II, Sao Paulo 01140-070, SP (Brazil); Weltman, Amanda, E-mail: amanda.weltman@uct.ac.za [Astrophysics, Cosmology & Gravity Center, Department of Mathematics and Applied Mathematics, University of Cape Town, Private Bag, Rondebosch 7700 (South Africa)

2015-07-30

We present a simple model where the effective cosmological constant appears from chameleon scalar fields. For a Kachru–Kallosh–Linde–Trivedi (KKLT)-inspired form of the potential and a particular chameleon coupling to the local density, patches of approximately constant scalar field potential cluster around regions of matter with density above a certain value, generating the effect of a cosmological constant on large scales. This construction addresses both the cosmological constant problem (why Λ is so small, yet nonzero) and the coincidence problem (why Λ is comparable to the matter density now)

On the constant-roll inflation

Science.gov (United States)

Yi, Zhu; Gong, Yungui

2018-03-01

The primordial power spectra of scalar and tensor perturbations during slow-roll inflation are usually calculated with the method of Bessel function approximation. For constant-roll or ultra slow-roll inflation, the method of Bessel function approximation may be invalid. We compare the numerical results with the analytical results derived from the Bessel function approximation, and we find that they differ significantly on super-horizon scales if the constant slow-roll parameter ηH is not small. More accurate method is needed for calculating the primordial power spectrum for constant-roll inflation.

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

GPR measurements of attenuation in concrete

Science.gov (United States)

Eisenmann, David; Margetan, Frank J.; Pavel, Brittney

2015-03-01

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

GPR measurements of attenuation in concrete

International Nuclear Information System (INIS)

Eisenmann, David; Margetan, Frank J.; Pavel, Brittney

2015-01-01

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

GPR measurements of attenuation in concrete

Energy Technology Data Exchange (ETDEWEB)

Eisenmann, David, E-mail: djeisen@cnde.iastate.edu; Margetan, Frank J., E-mail: djeisen@cnde.iastate.edu; Pavel, Brittney, E-mail: djeisen@cnde.iastate.edu [Center for Nondestructive Evaluation, Iowa State University, 1915 Scholl Road, Ames, IA 50011-3042 (United States)

2015-03-31

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

The fundamental constants a mystery of physics

CERN Document Server

Fritzsch, Harald

2009-01-01

The speed of light, the fine structure constant, and Newton's constant of gravity — these are just three among the many physical constants that define our picture of the world. Where do they come from? Are they constant in time and across space? In this book, physicist and author Harald Fritzsch invites the reader to explore the mystery of the fundamental constants of physics in the company of Isaac Newton, Albert Einstein, and a modern-day physicist

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)

Seismic Attenuation Tomography of the Rupture Zone of the 2010 Maule, Chile, Earthquake

Science.gov (United States)

Torpey, M. E.; Russo, R. M.; Panning, M. P.

2014-12-01

We used measurements of differential S to P seismic attenuation in the rupture zone of the 2010 Mw 8.8 Maule, Chile earthquake (33°S-38°S) to characterize the seismic attenuation structure of the South American crust and upper mantle wedge. We used data obtained from the IRIS CHAMP rapid-response temporary seismic network, filtered between 0.7-20 Hz. For events with large signal to noise ratios, we visually identified the P and S arrivals on the seismograms and used an evolving time window to determine 400 individual Qs and t* values and their uncertainties using a spectral ratio method. Using a phase pair method allows us to neglect the source-time function and instrument response of each P-S phase pair. Assuming a constant Qp/Qs ratio for a given P-S phase pair, we evaluated the 400 spectral ratios and discarded portions of the evolving time window that incorporate multipathed phases. We recalculated the Qs and standard deviation of the retained window and excluded measurements with standard deviations larger than half of the Qs value. We also excluded measurements that span frequency windows longer than 10 Hz as they contain noise that contaminates Qs measurements. We examined ~200 local events yielding a total of 1,076 path-integrated Q­s measurements. Qs values are low (100-400) for the majority of ray paths evaluated, however we observe a spatial distribution of low path-integrated Qs values (100-300) in the northeastern portion of the rupture zone and higher values (300-600) in the southwest. We divided the rupture zone into cubes and implemented a bounded linear inequality least squares inversion (0constant starting model of Qs=450 and solved for perturbations to the model using our observed δt* values and a radial-earth velocity model (IASPI91). Our ray coverage provides good resolution extending to depths of ~75 km in the mantle wedge.

Fat Attenuation at CT in Anorexia Nervosa

Science.gov (United States)

Gill, Corey M.; Torriani, Martin; Murphy, Rachel; Harris, Tamara B.; Miller, Karen K.; Klibanski, Anne

2016-01-01

Purpose To investigate the composition, cross-sectional area (CSA), and hormonal correlates of different fat depots in women with anorexia nervosa (AN) and control subjects with normal weights to find out whether patients with AN have lower fat CSA but higher attenuation than did control subjects and whether these changes may be mediated by gonadal steroids, cortisol, and thyroid hormones. Materials and Methods This study was institutional review board approved and HIPAA compliant. Written informed consent was obtained. Forty premenopausal women with AN and 40 normal-weight women of comparable age (mean age ± standard deviation, 26 years ± 5) were studied. All individuals underwent computed tomography of the abdomen and thigh with a calibration phantom. Abdominal subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), thigh SAT, and thigh intermuscular adipose tissue CSA and attenuation were quantified. Serum estradiol, thyroid hormones, and urinary free cortisol levels were assessed. Variables were compared by using analysis of variance. Associations were examined by using linear regression analysis. Results Women with AN had higher fat attenuation than did control subjects (−100.1 to −46.7 HU vs −117.6 to −61.8 HU, P < .0001), despite lower fat CSA (2.0–62.8 cm2 vs 5.5–185.9 cm2, P < .0001). VAT attenuation but not CSA was inversely associated with lowest prior lifetime body mass index in AN (r = −0.71, P = .006). Serum estradiol levels were inversely associated with fat attenuation (r = −0.34 to −0.61, P = .03 to <.0001) and were positively associated with fat CSA of all compartments (r = 0.42–0.64, P = .007 to <.0001). Thyroxine levels and urinary free cortisol levels were positively associated with thigh SAT attenuation (r = 0.64 [P = .006] and r = 0.68 [P = .0004], respectively) and were inversely associated with abdominal SAT and VAT CSA (r = −0.44 to −0.58, P = .04 to .02). Conclusion Women with AN have differences in fat

Constant Leverage And Constant Cost Of Capital: A Common Knowledge Half-Truth

Directory of Open Access Journals (Sweden)

Ignacio Vélez–Pareja

2008-04-01

In this document we show that for finite cash flows, Ke and hence WACC depend on the discount rate that is used to value the tax shield, TS and as expected, Ke and WACC are not constant with Kd as the discount rate for the tax shield, even if the leverage is constant. We illustrate this situation with a simple example. We analyze five methods: DCF using APV, FCF and traditional and general formulation for WACC, present value of CFE plus debt and Capital Cash Flow, CCF.

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.

A Short-Current Control Method for Constant Frequency Current-Fed Wireless Power Transfer Systems

Directory of Open Access Journals (Sweden)

Yanling Li

2017-04-01

Full Text Available Frequency drift is a serious problem in Current-Fed Wireless Power Transfer (WPT systems. When the operating frequency is drifting from the inherent Zero Voltage Switching (ZVS frequency of resonant network, large short currents will appear and damage the switches. In this paper, an inductance-dampening method is proposed to inhibit short currents and achieve constant-frequency operation. By adding a small auxiliary series inductance in the primary resonant network, short currents are greatly attenuated to a safe level. The operation principle and steady-state analysis of the system are provided. An overlapping time self-regulating circuit is designed to guarantee ZVS running. The range of auxiliary inductances is discussed and its critical value is calculated exactly. The design methodology is described and a design example is presented. Finally, a prototype is built and the experimental results verify the proposed method.

Attenuation Measurements in Solutions of Some Carbohydrates

International Nuclear Information System (INIS)

Gagandeep; Singh, Kulwant; Lark, B.S.; Sahota, H.S.

2000-01-01

The linear attenuation coefficients in aqueous solutions of three carbohydrates, glucose (C 6 H 12 O 6 ), maltose monohydrate (C 12 H 22 O 11 .H 2 O), and sucrose (C 12 H 22 O 11 ), were determined at 81, 356, 511, 662, 1173, and 1332 keV by the gamma-ray transmission method in a good geometry setup. From the precisely measured densities of these solutions, mass attenuation coefficients were then obtained that varied systematically with the corresponding changes in the concentrations (g/cm 3 ) of these solutions. The experimental results were used in terms of effective atomic numbers and electron densities. A comparison between experimental and theoretical values of attenuation coefficients has proven that the study has a potential application for the determination of attenuation coefficients of solid solutes from their solutions without obtaining them in pure crystalline form

A new technique to characterize CT scanner bow-tie filter attenuation and applications in human cadaver dosimetry simulations

Science.gov (United States)

Li, Xinhua; Shi, Jim Q.; Zhang, Da; Singh, Sarabjeet; Padole, Atul; Otrakji, Alexi; Kalra, Mannudeep K.; Xu, X. George; Liu, Bob

2015-01-01

Purpose: To present a noninvasive technique for directly measuring the CT bow-tie filter attenuation with a linear array x-ray detector. Methods: A scintillator based x-ray detector of 384 pixels, 307 mm active length, and fast data acquisition (model X-Scan 0.8c4-307, Detection Technology, FI-91100 Ii, Finland) was used to simultaneously detect radiation levels across a scan field-of-view. The sampling time was as short as 0.24 ms. To measure the body bow-tie attenuation on a GE Lightspeed Pro 16 CT scanner, the x-ray tube was parked at the 12 o’clock position, and the detector was centered in the scan field at the isocenter height. Two radiation exposures were made with and without the bow-tie in the beam path. Each readout signal was corrected for the detector background offset and signal-level related nonlinear gain, and the ratio of the two exposures gave the bow-tie attenuation. The results were used in the geant4 based simulations of the point doses measured using six thimble chambers placed in a human cadaver with abdomen/pelvis CT scans at 100 or 120 kV, helical pitch at 1.375, constant or variable tube current, and distinct x-ray tube starting angles. Results: Absolute attenuation was measured with the body bow-tie scanned at 80–140 kV. For 24 doses measured in six organs of the cadaver, the median or maximum difference between the simulation results and the measurements on the CT scanner was 8.9% or 25.9%, respectively. Conclusions: The described method allows fast and accurate bow-tie filter characterization. PMID:26520720

Bulk viscosity and ultrasonic attenuation in liquid metals

International Nuclear Information System (INIS)

Awasthi, O.N.; Murthy, B.V.S.

1984-11-01

Ultrasonic attenuation in simple liquid metals has been investigated using the thermodynamic theory of relaxation processes incorporating the concept of a two state model for the liquid near the melting point. Agreement of the results with the experimental values of the ultrasonic attenuation and bulk viscosity indicates that this might be an appropriate approach to explain the excess attenuation of ultrasonic waves in liquid metals. (author)

Spectrophotometric determination of association constant

DEFF Research Database (Denmark)

2016-01-01

Least-squares 'Systematic Trial-and-Error Procedure' (STEP) for spectrophotometric evaluation of association constant (equilibrium constant) K and molar absorption coefficient E for a 1:1 molecular complex, A + B = C, with error analysis according to Conrow et al. (1964). An analysis of the Charge...

Constant strength fuel-fuel cell

International Nuclear Information System (INIS)

Vaseen, V.A.

1980-01-01

A fuel cell is an electrochemical apparatus composed of both a nonconsumable anode and cathode; and electrolyte, fuel oxidant and controls. This invention guarantees the constant transfer of hydrogen atoms and their respective electrons, thus a constant flow of power by submergence of the negative electrode in a constant strength hydrogen furnishing fuel; when said fuel is an aqueous absorbed hydrocarbon, such as and similar to ethanol or methnol. The objective is accomplished by recirculation of the liquid fuel, as depleted in the cell through specific type membranes which pass water molecules and reject the fuel molecules; thus concentrating them for recycle use

Effect of collimator size and absorber thickness on soil bulk density evaluation by gamma-ray attenuation

International Nuclear Information System (INIS)

Costa, J.C.; Borges, J.A.R.; Pires, L.F.

2014-01-01

Representative measurements of the soil bulk density (ρ s ) can be affected depending on the geometry selected for gamma-ray attenuation (GRA) measurements. In this study, the effect of collimator size (2–4 mm diameters) and absorber thickness (2–15 cm) on ρ s measurements of sandy and clayey soils was investigated. In summary, the results obtained for the 137 Cs show that ρ s remained fairly constant for values of thickness larger than 7 cm (both soils). The very same result was observed for collimator sizes 2–4 mm. Regarding the 241 Am source, ρ s values presented variations with the collimator size (both soils) for the different thicknesses. The best values of ρ s were obtained for samples smaller than 5 cm and also for the small collimator diameters. - Highlights: ► Representative measurements of the soil bulk density by gamma-ray attenuation. ► For 137 Cs the best bulk density values were obtained for samples larger than 7 cm. ► For 241 Am the best bulk density values were obtained for samples smaller than 5 cm

Arbitrary Control of Polarization and Intensity Profiles of Diffraction-Attenuation-Resistant Beams along the Propagation Direction

Science.gov (United States)

Corato-Zanarella, Mateus; Dorrah, Ahmed H.; Zamboni-Rached, Michel; Mojahedi, Mo

2018-02-01

We report on the theory and experimental generation of a class of diffraction-attenuation-resistant beams with state of polarization (SOP) and intensity that can be controlled on demand along the propagation direction. This control is achieved by a suitable superposition of Bessel beams, whose parameters are systematically chosen based on closed-form analytic expressions provided by the frozen waves method. Using an amplitude-only spatial light modulator, we experimentally demonstrate three scenarios. In the first, the SOP of a horizontally polarized beam evolves to radial polarization and is then changed to vertical polarization, with the beam intensity held constant. In the second, we simultaneously control the SOP and the longitudinal intensity profile, which is chosen such that the beam's central ring can be switched off over predefined space regions, thus generating multiple foci with different SOPs and at different intensity levels along the propagation. Finally, the ability to control the SOP while overcoming attenuation inside lossy fluids is shown experimentally. We envision our proposed method to be of great interest for many applications, such as optical tweezers, atom guiding, material processing, microscopy, and optical communications.

Universe of constant

Science.gov (United States)

Yongquan, Han

2016-10-01

The ideal gas state equation is not applicable to ordinary gas, it should be applied to the Electromagnetic ``gas'' that is applied to the radiation, the radiation should be the ultimate state of matter changes or initial state, the universe is filled with radiation. That is, the ideal gas equation of state is suitable for the Singular point and the universe. Maybe someone consider that, there is no vessel can accommodate radiation, it is because the Ordinary container is too small to accommodate, if the radius of your container is the distance that Light through an hour, would you still think it can't accommodates radiation? Modern scientific determinate that the radius of the universe now is about 1027 m, assuming that the universe is a sphere whose volume is approximately: V = 4.19 × 1081 cubic meters, the temperature radiation of the universe (cosmic microwave background radiation temperature of the universe, should be the closest the average temperature of the universe) T = 3.15k, radiation pressure P = 5 × 10-6 N / m 2, according to the law of ideal gas state equation, PV / T = constant = 6 × 1075, the value of this constant is the universe, The singular point should also equal to the constant Author: hanyongquan

An attenuation measurement technique for rotating planar detector positron tomographs

International Nuclear Information System (INIS)

McNeil, P.A.; Julyan, P.J.; Parker, D.J.

1997-01-01

This paper presents a new attenuation measurement technique suitable for rotating planar detector positron tomographs. Transmission measurements are made using two unshielded positron-emitting line sources, one attached to the front face of each detector. Many of the scattered and accidental coincidences are rejected by including only those coincidences that form a vector passing within a predetermined distance of either line source. Some scattered and accidental coincidences are still included, which reduces the measured linear attenuation; in principle their contribution can be accurately estimated and subtracted, but in practice, when limited statistics are available (as is the case with the multi-wire Birmingham positron camera), this background subtraction unacceptably increases the noise. Instead an attenuation image having the correct features can be reconstructed from the measured projections. For objects containing only a few discrete linear attenuation coefficients, segmentation of this attenuation image reduces noise and allows the correct linear attenuation coefficients to be restored by renormalization. Reprojection through the segmented image may then provide quantitatively correct attenuation correction factors of sufficient statistical quality to correct for attenuation in PET emission images. (author)

Characteristics of Earthquake Ground Motion Attenuation in Korea and Japan

International Nuclear Information System (INIS)

Choi, In-Kil; Choun, Young-Sun; Nakajima, Masato; Ohtori, Yasuki; Yun, Kwan-Hee

2006-01-01

The characteristics of a ground motion attenuation in Korea and Japan were estimated by using the earthquake ground motions recorded at the equal distance observation station by KMA, K-NET and KiK-net of Korea and Japan. The ground motion attenuation equations proposed for Korea and Japan were evaluated by comparing the predicted value for the Fukuoka earthquake with the observed records. The predicted values from the attenuation equations show a good agreement with the observed records and each other. It can be concluded from this study that the ground motion attenuation equations can be used for the prediction of strong ground motion attenuation and for an evaluation of the attenuation equations proposed for Korea

Measurements of earplug attenuation under supra-aural and circumaural headphones.

Science.gov (United States)

Tufts, Jennifer B; Palmer, Jillian V; Marshall, Lynne

2012-10-01

Supra-aural audiometric headphones are generally not recommended for use in measuring the attenuation of earplugs, because contact between the headphone and pinna and/or earplug could alter the attenuation obtained, and because of concerns of non-comparability between modes of excitation from supra-aural headphones and the sound-field procedure required by the standardized method. In this study, we compared measurements of earplug attenuation obtained under Telephonics TDH-50P supra-aural headphones with measurements obtained under circumaural headphones designed expressly for such testing. The attenuation of three types of earplugs (foam, premolded quadruple-flange, and custom-molded) was measured in a repeated-measures design. The study sample comprised 42 normal-hearing adults (21 females, 21 males). With the foam earplugs, nearly all of the attenuation measurements under the supra-aural headphones fell within 10 dB of the measurements under the circumaural headphones. With the flange and custom earplugs, approximately 10% of individuals obtained spuriously high attenuation under the supra-aural headphones. We conclude that standard supra-aural audiometric headphones are suitable for measuring the attenuation provided by foam earplugs. However, supra-aural headphones should not be used to measure the attenuation of flange or custom-molded earplugs. The potential exists for substantial over-estimation of attenuation, especially of custom plugs.

Attenuation measurements in solutions of some carbohydrates

International Nuclear Information System (INIS)

Gagandeep; Singh, K.; Lark, B.S.; Sahota, H.S.

2000-01-01

The linear attenuation coefficients in aqueous solutions of three carbohydrates, glucose (C 6 H 12 O 6 ), maltose monohydrate (C 12 H 22 O 11 ·H 2 O), and sucrose (C 12 H 22 O 11 ), were determined at 81, 356, 511, 662, 1,173, and 1,332 keV by the gamma-ray transmission method in a good geometry setup. From the precisely measured densities of these solutions, mass attenuation coefficients were then obtained that varied systematically with the corresponding changes in the concentrations (g/cm 3 ) of these solutions. The experimental results were used in terms of effective atomic numbers and electron densities. A comparison between experimental and theoretical values of attenuation coefficients has proven that the study has a potential application for the determination of attenuation coefficients of solid solutes from their solutions without obtaining them in pure crystalline form

Larson-Miller Constant of Heat-Resistant Steel

Science.gov (United States)

Tamura, Manabu; Abe, Fujio; Shiba, Kiyoyuki; Sakasegawa, Hideo; Tanigawa, Hiroyasu

2013-06-01

Long-term rupture data for 79 types of heat-resistant steels including carbon steel, low-alloy steel, high-alloy steel, austenitic stainless steel, and superalloy were analyzed, and a constant for the Larson-Miller (LM) parameter was obtained in the current study for each material. The calculated LM constant, C, is approximately 20 for heat-resistant steels and alloys except for high-alloy martensitic steels with high creep resistance, for which C ≈ 30 . The apparent activation energy was also calculated, and the LM constant was found to be proportional to the apparent activation energy with a high correlation coefficient, which suggests that the LM constant is a material constant possessing intrinsic physical meaning. The contribution of the entropy change to the LM constant is not small, especially for several martensitic steels with large values of C. Deformation of such martensitic steels should accompany a large entropy change of 10 times the gas constant at least, besides the entropy change due to self-diffusion.

Constant exposure technique in industrial radiography

International Nuclear Information System (INIS)

Domanus, J.C.

1983-08-01

The principles and advantages of the constant exposure technique are explained. Choice of exposure factors is analyzed. Film, paper and intensifying screens used throughout the investigation and film and paper processing are described. Exposure technique and the use of image quality indicators are given. Methods of determining of radiographic image quality are presented. Conclusions about the use of constant exposure vs. constant kilovoltage technique are formulated. (author)

Mirtazapine attenuates cocaine seeking in rats.

Science.gov (United States)

Barbosa-Méndez, Susana; Leff, Phillipe; Arías-Caballero, Adriana; Hernández-Miramontes, Ricardo; Heinze, Gerardo; Salazar-Juárez, Alberto

2017-09-01

Relapse to cocaine use is a major problem in the clinical treatment of cocaine addiction. Antidepressants have been studied for their therapeutic potential to treat cocaine use disorder. Research has suggested that antidepressants attenuate both drug craving and the re-acquisition of drug-seeking and drug-taking behaviors. This study examined the efficacy of mirtazapine, an antidepressant/anxiolytic, in decreasing cocaine seeking in rats. We used the cocaine self-administration paradigm to assess the effects of mirtazapine on rats trained to self-administer cocaine or food under a fixed-ratio schedule. Mirtazapine (30 mg/kg, i.p.) was administered during extinction. Mirtazapine significantly attenuated non-reinforced lever-press responses during extinction. Moreover, the mirtazapine dosed for 30 days during extinction produced sustained attenuation of lever-press responses during re-acquisition of cocaine self-administration, without changing food-seeking behavior. Our results showed that mirtazapine attenuated the re-acquisition of cocaine-seeking responses. Our study pointed to the efficacy of mirtazapine in reducing the risk of drug relapse during abstinence, suggesting for its potential use as a novel pharmacological agent to treat drug abuse. Copyright © 2017 Elsevier Ltd. All rights reserved.

Cosmological constant--the weight of the vacuum

International Nuclear Information System (INIS)

Padmanabhan, T.

2003-01-01

Recent cosmological observations suggest the existence of a positive cosmological constant Λ with the magnitude Λ(Gℎ/c 3 )∼10 -123 . This review discusses several aspects of the cosmological constant both from the cosmological (Sections 1-6) and field theoretical (Sections 7-11) perspectives. After a brief introduction to the key issues related to cosmological constant and a historical overview, a summary of the kinematics and dynamics of the standard Friedmann model of the universe is provided. The observational evidence for cosmological constant, especially from the supernova results, and the constraints from the age of the universe, structure formation, Cosmic Microwave Background Radiation (CMBR) anisotropies and a few others are described in detail, followed by a discussion of the theoretical models (quintessence, tachyonic scalar field, ...) from different perspectives. The latter part of the review (Sections 7-11) concentrates on more conceptual and fundamental aspects of the cosmological constant like some alternative interpretations of the cosmological constant, relaxation mechanisms to reduce the cosmological constant to the currently observed value, the geometrical structure of the de Sitter spacetime, thermodynamics of the de Sitter universe and the role of string theory in the cosmological constant problem

Radiographic constant exposure technique

DEFF Research Database (Denmark)

Domanus, Joseph Czeslaw

1985-01-01

The constant exposure technique has been applied to assess various industrial radiographic systems. Different X-ray films and radiographic papers of two producers were compared. Special attention was given to fast film and paper used with fluorometallic screens. Radiographic image quality...... was tested by the use of ISO wire IQI's and ASTM penetrameters used on Al and Fe test plates. Relative speed and reduction of kilovoltage obtained with the constant exposure technique were calculated. The advantages of fast radiographic systems are pointed out...

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)

Constant-roll tachyon inflation and observational constraints

Science.gov (United States)

Gao, Qing; Gong, Yungui; Fei, Qin

2018-05-01

For the constant-roll tachyon inflation, we derive the analytical expressions for the scalar and tensor power spectra, the scalar and tensor spectral tilts and the tensor to scalar ratio to the first order of epsilon1 by using the method of Bessel function approximation. The derived ns-r results are compared with the observations, we find that only the constant-roll inflation with ηH being a constant is consistent with the observations and observations constrain the constant-roll inflation to be slow-roll inflation. The tachyon potential is also reconstructed for the constant-roll inflation which is consistent with the observations.

Graviton fluctuations erase the cosmological constant

Science.gov (United States)

Wetterich, C.

2017-10-01

Graviton fluctuations induce strong non-perturbative infrared renormalization effects for the cosmological constant. The functional renormalization flow drives a positive cosmological constant towards zero, solving the cosmological constant problem without the need to tune parameters. We propose a simple computation of the graviton contribution to the flow of the effective potential for scalar fields. Within variable gravity, with effective Planck mass proportional to the scalar field, we find that the potential increases asymptotically at most quadratically with the scalar field. The solutions of the derived cosmological equations lead to an asymptotically vanishing cosmological "constant" in the infinite future, providing for dynamical dark energy in the present cosmological epoch. Beyond a solution of the cosmological constant problem, our simplified computation also entails a sizeable positive graviton-induced anomalous dimension for the quartic Higgs coupling in the ultraviolet regime, substantiating the successful prediction of the Higgs boson mass within the asymptotic safety scenario for quantum gravity.

Josephson tunnel junction microwave attenuator

DEFF Research Database (Denmark)

Koshelets, V. P.; Shitov, S. V.; Shchukin, A. V.

1993-01-01

A new element for superconducting electronic circuitry-a variable attenuator-has been proposed, designed, and successfully tested. The principle of operation is based on the change in the microwave impedance of a superconductor-insulator-superconductor (SIS) Josephson tunnel junction when dc biased...... at different points in the current-voltage characteristic. Both numerical calculations based on the Tien-Gordon theory and 70-GHz microwave experiments have confirmed the wide dynamic range (more than 15-dB attenuation for one stage) and the low insertion loss in the ''open'' state. The performance of a fully...

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 ...

Attenuation correction strategies for multi-energy photon emitters using SPECT

International Nuclear Information System (INIS)

Pretorius, P.H.; King, M.A.; Pan, T.S.

1996-01-01

The aim of this study was to investigate whether the photopeak window projections from different energy photons can be combined into a single window for reconstruction or if it is better to not combine the projections due to differences in the attenuation maps required for each photon energy. The mathematical cardiac torso (MCAT) phantom was modified to simulate the uptake of Ga-67 in the human body. Four spherical hot tumors were placed in locations which challenged attenuation correction. An analytical 3D projector with attenuation and detector response included was used to generate projection sets. Data were reconstructed using filtered backprojection (FBP) reconstruction with Butterworth filtering in conjunction with one iteration of Chang attenuation correction, and with 5 and 10 iterations of ordered-subset maximum-likelihood expectation-maximization reconstruction. To serve as a standard for comparison, the projection sets obtained from the two energies were first reconstructed separately using their own attenuation maps. The emission data obtained from both energies were added and reconstructed using the following attenuation strategies: (1) the 93 keV attenuation map for attenuation correction, (2) the 185 keV attenuation map for attenuation correction, (3) using a weighted mean obtained from combining the 93 keV and 185 keV maps, and (4) an ordered subset approach which combines both energies. The central count ratio (CCR) and total count ratio (TCR) were used to compare the performance of the different strategies. Compared to the standard method, results indicate an over-estimation with strategy 1, an under-estimation with strategy 2 and comparable results with strategies 3 and 4. In all strategies, the CCR's of sphere 4 were under-estimated, although TCR's were comparable to that of the other locations. The weighted mean and ordered subset strategies for attenuation correction were of comparable accuracy to reconstruction of the windows separately

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

CODATA recommended values of the fundamental constants

International Nuclear Information System (INIS)

Mohr, Peter J.; Taylor, Barry N.

2000-01-01

A review is given of the latest Committee on Data for Science and Technology (CODATA) adjustment of the values of the fundamental constants. The new set of constants, referred to as the 1998 values, replaces the values recommended for international use by CODATA in 1986. The values of the constants, and particularly the Rydberg constant, are of relevance to the calculation of precise atomic spectra. The standard uncertainty (estimated standard deviation) of the new recommended value of the Rydberg constant, which is based on precision frequency metrology and a detailed analysis of the theory, is approximately 1/160 times the uncertainty of the 1986 value. The new set of recommended values as well as a searchable bibliographic database that gives citations to the relevant literature is available on the World Wide Web at physics.nist.gov/constants and physics.nist.gov/constantsbib, respectively

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

Post-Retrieval Extinction Attenuates Cocaine Memories

OpenAIRE

Sartor, Gregory C; Aston-Jones, Gary

2013-01-01

Recent studies have shown that post-retrieval extinction training attenuates fear and reward-related memories in both humans and rodents. This noninvasive, behavioral approach has the potential to be used in clinical settings to treat maladaptive memories that underlie several psychiatric disorders, including drug addiction. However, few studies to date have used a post-retrieval extinction approach to attenuate addiction-related memories. In the current study, we attempted to disrupt cocaine...

The Dielectric Constant of Lubrication Oils

National Research Council Canada - National Science Library

Carey, A

1998-01-01

The values of the dielectric constant of simple molecules is discussed first, along with the relationship between the dielectric constant and other physical properties such as boiling point, melting...

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.

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.

A promising hybrid approach to SPECT attenuation correction

International Nuclear Information System (INIS)

Lewis, N.H.; Faber, T.L.; Corbett, J.R.; Stokely, E.M.

1984-01-01

Most methods for attenuation compensation in SPECT either rely on the assumption of uniform attenuation, or use slow iteration to achieve accuracy. However, hybrid methods that combine iteration with simple multiplicative correction can accommodate nonuniform attenuation, and such methods converge faster than other iterative techniques. The authors evaluated two such methods, which differ in use of a damping factor to control convergence. Both uniform and nonuniform attenuation were modeled, using simulated and phantom data for a rotating gamma camera. For simulations done with 360 0 data and the correct attenuation map, activity levels were reconstructed to within 5% of the correct values after one iteration. Using 180 0 data, reconstructed levels in regions representing lesion and background were within 5% of the correct values in three iterations; however, further iterations were needed to eliminate the characteristic streak artifacts. The damping factor had little effect on 360 0 reconstruction, but was needed for convergence with 180 0 data. For both cold- and hot-lesion models, image contrast was better from the hybrid methods than from the simpler geometric-mean corrector. Results from the hybrid methods were comparable to those obtained using the conjugate-gradient iterative method, but required 50-100% less reconstruction time. The relative speed of the hybrid methods, and their accuracy in reconstructing photon activity in the presence of nonuniform attenuation, make them promising tools for quantitative SPECT reconstruction

New perspectives on constant-roll inflation

Science.gov (United States)

Cicciarella, Francesco; Mabillard, Joel; Pieroni, Mauro

2018-01-01

We study constant-roll inflation using the β-function formalism. We show that the constant rate of the inflaton roll is translated into a first order differential equation for the β-function which can be solved easily. The solutions to this equation correspond to the usual constant-roll models. We then construct, by perturbing these exact solutions, more general classes of models that satisfy the constant-roll equation asymptotically. In the case of an asymptotic power law solution, these corrections naturally provide an end to the inflationary phase. Interestingly, while from a theoretical point of view (in particular in terms of the holographic interpretation) these models are intrinsically different from standard slow-roll inflation, they may have phenomenological predictions in good agreement with present cosmological data.

The fine-structure constant before quantum mechanics

International Nuclear Information System (INIS)

Kragh, Helge

2003-01-01

This paper focuses on the early history of the fine-structure constant, largely the period until 1925. Contrary to what is generally assumed, speculations concerning the interdependence of the elementary electric charge and Planck's constant predated Arnold Sommerfeld's 1916 discussion of the dimensionless constant. This paper pays particular attention to a little known work from 1914 in which G N Lewis and E Q Adams derived what is effectively a numerical expression for the fine-structure constant

Stability constants of scandium complexes, 1

International Nuclear Information System (INIS)

Itoh, Hisako; Itoh, Naomi; Suzuki, Yasuo

1984-01-01

The stability constants of scandium complexes with some carboxylate ligands were determined potentiometrically at 25.0 and 40.0 0 C and at an ionic strength of 0.10 with potassium nitrate as supporting electrolyte. The constants of the scandium complexes were appreciably greater than those of the corresponding lanthanoid complexes, as expected. The changes in free energy, enthalpy, and entropy for the formation of the scandium complexes were calculated from the stability constants at two temperatures. (author)

Zero cosmological constant from normalized general relativity

International Nuclear Information System (INIS)

Davidson, Aharon; Rubin, Shimon

2009-01-01

Normalizing the Einstein-Hilbert action by the volume functional makes the theory invariant under constant shifts in the Lagrangian. The associated field equations then resemble unimodular gravity whose otherwise arbitrary cosmological constant is now determined as a Machian universal average. We prove that an empty space-time is necessarily Ricci tensor flat, and demonstrate the vanishing of the cosmological constant within the scalar field paradigm. The cosmological analysis, carried out at the mini-superspace level, reveals a vanishing cosmological constant for a universe which cannot be closed as long as gravity is attractive. Finally, we give an example of a normalized theory of gravity which does give rise to a non-zero cosmological constant.

The time constant of the somatogravic illusion.

Science.gov (United States)

Correia Grácio, B J; de Winkel, K N; Groen, E L; Wentink, M; Bos, J E

2013-02-01

Without visual feedback, humans perceive tilt when experiencing a sustained linear acceleration. This tilt illusion is commonly referred to as the somatogravic illusion. Although the physiological basis of the illusion seems to be well understood, the dynamic behavior is still subject to discussion. In this study, the dynamic behavior of the illusion was measured experimentally for three motion profiles with different frequency content. Subjects were exposed to pure centripetal accelerations in the lateral direction and were asked to indicate their tilt percept by means of a joystick. Variable-radius centrifugation during constant angular rotation was used to generate these motion profiles. Two self-motion perception models were fitted to the experimental data and were used to obtain the time constant of the somatogravic illusion. Results showed that the time constant of the somatogravic illusion was on the order of two seconds, in contrast to the higher time constant found in fixed-radius centrifugation studies. Furthermore, the time constant was significantly affected by the frequency content of the motion profiles. Motion profiles with higher frequency content revealed shorter time constants which cannot be explained by self-motion perception models that assume a fixed time constant. Therefore, these models need to be improved with a mechanism that deals with this variable time constant. Apart from the fundamental importance, these results also have practical consequences for the simulation of sustained accelerations in motion simulators.

An Einstein-Cartan Fine Structure Constant Definition

Directory of Open Access Journals (Sweden)

Stone R. A. Jr.

2010-01-01

Full Text Available The fine structure constant definition given in Stone R.A. Jr. Progress in Physics, 2010, v.1, 11-13 is compared to an Einstein-Cartan fine structure constant definition. It is shown that the Einstein-Cartan definition produces the correct pure theory value, just not the measure value. To produce the measured value, the pure theory Einstein-Cartan fine structure constant requires only the new variables and spin coupling of the fine structure constant definition in [1].

Factors influencing seismic wave attenuation in the lithosphere in continental rift zones

Directory of Open Access Journals (Sweden)

А. А. Dobrynina

2017-01-01

Full Text Available Attenuation of seismic waves in the crust and the upper mantle has been studied in three global rift systems: the Baikal rift system (Eurasia, the North Tanzanian divergence zone (Africa and the Basin and Range Province (North America. Using the records of direct and coda waves of regional earthquakes, the single scattering theory [Aki, Chouet, 1975], the hybrid model from [Zeng, 1991] and the approach described in [Wennerberg, 1993], we estimated the seismic quality factor (QC, frequency parameter (n, attenuation coefficient (δ, and total attenuation (QT. In addition, we evaluated the contributions of two components into total attenuation: intrinsic attenuation (Qi, and scattering attenuation (Qsc. Values of QC are strongly dependent on the frequency within the range of 0.2–16 Hz, as well as on the length of the coda processing window. The observed increase of QC with larger lengths of the coda processing window can be interpreted as a decrease in attenuation with increasing depth. Having compared the depth variations in the attenuation coefficient (δ and the frequency (n with the velocity structures of the studied regions, we conclude that seismic wave attenuation changes at the velocity boundaries in the medium. Moreover, the comparison results show that the estimated variations in the attenuation parameters with increasing depth are considerably dependent on utilized velocity models of the medium. Lateral variations in attenuation of seismic waves correlate with the geological and geophysical characteristics of the regions, and attenuation is primarily dependent on the regional seismic activity and regional heat flow. The geological inhomogeneities of the medium and the age of crust consolidation are secondary factors. Our estimations of intrinsic attenuation (Qi and scattering attenuation (Qsc show that in all the three studied regions, intrinsic attenuation is the major contributor to total attenuation. Our study shows that the

STABILITY CONSTANT OF THE TRISGLYCINATO METAL ...

African Journals Online (AJOL)

DR. AMINU

overall stability constants of the complexes were found to be similar. Keywords: Glycinato, titration ... +. −. = 1 where Ka = dissociation constant of the amino acid. [ ]+. H = concentration of the .... Synthesis and techniques in inorganic chemistry.

Interacting universes and the cosmological constant

International Nuclear Information System (INIS)

Alonso-Serrano, A.; Bastos, C.; Bertolami, O.; Robles-Pérez, S.

2013-01-01

In this Letter it is studied the effects that an interaction scheme among universes can have in the values of their cosmological constants. In the case of two interacting universes, the value of the cosmological constant of one of the universes becomes very close to zero at the expense of an increasing value of the cosmological constant of the partner universe. In the more general case of a chain of N interacting universes with periodic boundary conditions, the spectrum of the Hamiltonian splits into a large number of levels, each of them associated with a particular value of the cosmological constant, that can be occupied by single universes revealing a collective behavior that plainly shows that the multiverse is much more than the mere sum of its parts

Interacting universes and the cosmological constant

Energy Technology Data Exchange (ETDEWEB)

Alonso-Serrano, A. [Centro de Física “Miguel Catalán”, Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 121, 28006 Madrid (Spain); Estación Ecológica de Biocosmología, Pedro de Alvarado 14, 06411 Medellín (Spain); Bastos, C. [Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Avenida Rovisco Pais 1, 1049-001 Lisboa (Portugal); Bertolami, O. [Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Avenida Rovisco Pais 1, 1049-001 Lisboa (Portugal); Departamento de Física e Astronomia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal); Robles-Pérez, S., E-mail: salvarp@imaff.cfmac.csic.es [Centro de Física “Miguel Catalán”, Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 121, 28006 Madrid (Spain); Estación Ecológica de Biocosmología, Pedro de Alvarado 14, 06411 Medellín (Spain); Física Teórica, Universidad del País Vasco, Apartado 644, 48080 Bilbao (Spain)

2013-02-12

In this Letter it is studied the effects that an interaction scheme among universes can have in the values of their cosmological constants. In the case of two interacting universes, the value of the cosmological constant of one of the universes becomes very close to zero at the expense of an increasing value of the cosmological constant of the partner universe. In the more general case of a chain of N interacting universes with periodic boundary conditions, the spectrum of the Hamiltonian splits into a large number of levels, each of them associated with a particular value of the cosmological constant, that can be occupied by single universes revealing a collective behavior that plainly shows that the multiverse is much more than the mere sum of its parts.

Solar constant values for estimating solar radiation

International Nuclear Information System (INIS)

Li, Huashan; Lian, Yongwang; Wang, Xianlong; Ma, Weibin; Zhao, Liang

2011-01-01

There are many solar constant values given and adopted by researchers, leading to confusion in estimating solar radiation. In this study, some solar constant values collected from literature for estimating solar radiation with the Angstroem-Prescott correlation are tested in China using the measured data between 1971 and 2000. According to the ranking method based on the t-statistic, a strategy to select the best solar constant value for estimating the monthly average daily global solar radiation with the Angstroem-Prescott correlation is proposed. -- Research highlights: → The effect of the solar constant on estimating solar radiation is investigated. → The investigation covers a diverse range of climate and geography in China. → A strategy to select the best solar constant for estimating radiation is proposed.

Capacitive Cells for Dielectric Constant Measurement

Science.gov (United States)

Aguilar, Horacio Munguía; Maldonado, Rigoberto Franco

2015-01-01

A simple capacitive cell for dielectric constant measurement in liquids is presented. As an illustrative application, the cell is used for measuring the degradation of overheated edible oil through the evaluation of their dielectric constant.

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.

Determination of beta attenuation coefficients by means of timing method

International Nuclear Information System (INIS)

Ermis, E.E.; Celiktas, C.

2012-01-01

Highlights: ► Beta attenuation coefficients of absorber materials were found in this study. ► For this process, a new method (timing method) was suggested. ► The obtained beta attenuation coefficients were compatible with the results from the traditional one. ► The timing method can be used to determine beta attenuation coefficient. - Abstract: Using a counting system with plastic scintillation detector, beta linear and mass attenuation coefficients were determined for bakelite, Al, Fe and plexiglass absorbers by means of timing method. To show the accuracy and reliability of the obtained results through this method, the coefficients were also found via conventional energy method. Obtained beta attenuation coefficients from both methods were compared with each other and the literature values. Beta attenuation coefficients obtained through timing method were found to be compatible with the values obtained from conventional energy method and the literature.

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 of trace organic compounds (TOrCs) inbioelectrochemical systems

KAUST Repository

Werner, Craig M.

2015-04-01

Microbial fuel cells (MFCs) and microbial electrolysis cells (MECs) are two types of microbial bioelectrochemical systems (BESs) that use microorganisms to convert chemical energy in wastewaters into useful energy products such as (bio)electricity (MFC) or hydrogen gas (MEC). These two systems were evaluated for their capacity to attenuate trace organic compounds (TOrCs), commonly found in municipal wastewater, under closed circuit (current generation) and open circuit (no current generation) conditions, using acetate as the carbon source. A biocide was used to evaluate attenuation in terms of biotransformation versus sorption. The difference in attenuation observed before and after addition of the biocide represented biotransformation, while attenuation after addition of a biocide primarily indicated sorption. Attenuation of TOrCs was similar in MFCs and MECs for eight different TOrCs, except for caffeine and trimethoprim where slightly higher attenuation was observed in MECs. Electric current generation did not enhance attenuation of the TOrCs except for caffeine, which showed slightly higher attenuation under closed circuit conditions in both MFCs and MECs. Substantial sorption of the TOrCs occurred to the biofilm-covered electrodes, but no consistent trend could be identified regarding the physico-chemical properties of the TOrCs tested and the extent of sorption. The octanol-water distribution coefficient at pH 7.4 (log DpH 7.4) appeared to be a reasonable predictor for sorption of some of the compounds (carbamazepine, atrazine, tris(2-chloroethyl) phosphate and diphenhydramine) but not for others (N,N-Diethyl-meta-toluamide). Atenolol also showed high levels of sorption despite being the most hydrophilic in the suite of compounds studied (log DpH 7.4=-1.99). Though BESs do not show any inherent advantages over conventional wastewater treatment, with respect to TOrC removal, overall removals in BESs are similar to that reported for conventional wastewater

Active inference, sensory attenuation and illusions.

Science.gov (United States)

Brown, Harriet; Adams, Rick A; Parees, Isabel; Edwards, Mark; Friston, Karl

2013-11-01

Active inference provides a simple and neurobiologically plausible account of how action and perception are coupled in producing (Bayes) optimal behaviour. This can be seen most easily as minimising prediction error: we can either change our predictions to explain sensory input through perception. Alternatively, we can actively change sensory input to fulfil our predictions. In active inference, this action is mediated by classical reflex arcs that minimise proprioceptive prediction error created by descending proprioceptive predictions. However, this creates a conflict between action and perception; in that, self-generated movements require predictions to override the sensory evidence that one is not actually moving. However, ignoring sensory evidence means that externally generated sensations will not be perceived. Conversely, attending to (proprioceptive and somatosensory) sensations enables the detection of externally generated events but precludes generation of actions. This conflict can be resolved by attenuating the precision of sensory evidence during movement or, equivalently, attending away from the consequences of self-made acts. We propose that this Bayes optimal withdrawal of precise sensory evidence during movement is the cause of psychophysical sensory attenuation. Furthermore, it explains the force-matching illusion and reproduces empirical results almost exactly. Finally, if attenuation is removed, the force-matching illusion disappears and false (delusional) inferences about agency emerge. This is important, given the negative correlation between sensory attenuation and delusional beliefs in normal subjects--and the reduction in the magnitude of the illusion in schizophrenia. Active inference therefore links the neuromodulatory optimisation of precision to sensory attenuation and illusory phenomena during the attribution of agency in normal subjects. It also provides a functional account of deficits in syndromes characterised by false inference

Constant conditional entropy and related hypotheses

International Nuclear Information System (INIS)

Ferrer-i-Cancho, Ramon; Dębowski, Łukasz; Moscoso del Prado Martín, Fermín

2013-01-01

Constant entropy rate (conditional entropies must remain constant as the sequence length increases) and uniform information density (conditional probabilities must remain constant as the sequence length increases) are two information theoretic principles that are argued to underlie a wide range of linguistic phenomena. Here we revise the predictions of these principles in the light of Hilberg’s law on the scaling of conditional entropy in language and related laws. We show that constant entropy rate (CER) and two interpretations for uniform information density (UID), full UID and strong UID, are inconsistent with these laws. Strong UID implies CER but the reverse is not true. Full UID, a particular case of UID, leads to costly uncorrelated sequences that are totally unrealistic. We conclude that CER and its particular cases are incomplete hypotheses about the scaling of conditional entropies. (letter)

Systematics of constant roll inflation

Science.gov (United States)

Anguelova, Lilia; Suranyi, Peter; Wijewardhana, L. C. R.

2018-02-01

We study constant roll inflation systematically. This is a regime, in which the slow roll approximation can be violated. It has long been thought that this approximation is necessary for agreement with observations. However, recently it was understood that there can be inflationary models with a constant, and not necessarily small, rate of roll that are both stable and compatible with the observational constraint ns ≈ 1. We investigate systematically the condition for such a constant-roll regime. In the process, we find a whole new class of inflationary models, in addition to the known solutions. We show that the new models are stable under scalar perturbations. Finally, we find a part of their parameter space, in which they produce a nearly scale-invariant scalar power spectrum, as needed for observational viability.

Reactor group constants and benchmark test

Energy Technology Data Exchange (ETDEWEB)

Takano, Hideki [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

2001-08-01

The evaluated nuclear data files such as JENDL, ENDF/B-VI and JEF-2 are validated by analyzing critical mock-up experiments for various type reactors and assessing applicability for nuclear characteristics such as criticality, reaction rates, reactivities, etc. This is called Benchmark Testing. In the nuclear calculations, the diffusion and transport codes use the group constant library which is generated by processing the nuclear data files. In this paper, the calculation methods of the reactor group constants and benchmark test are described. Finally, a new group constants scheme is proposed. (author)

Inflation with a constant rate of roll

International Nuclear Information System (INIS)

Motohashi, Hayato; Starobinsky, Alexei A.; Yokoyama, Jun'ichi

2015-01-01

We consider an inflationary scenario where the rate of inflaton roll defined by ·· φ/H φ-dot remains constant. The rate of roll is small for slow-roll inflation, while a generic rate of roll leads to the interesting case of 'constant-roll' inflation. We find a general exact solution for the inflaton potential required for such inflaton behaviour. In this model, due to non-slow evolution of background, the would-be decaying mode of linear scalar (curvature) perturbations may not be neglected. It can even grow for some values of the model parameter, while the other mode always remains constant. However, this always occurs for unstable solutions which are not attractors for the given potential. The most interesting particular cases of constant-roll inflation remaining viable with the most recent observational data are quadratic hilltop inflation (with cutoff) and natural inflation (with an additional negative cosmological constant). In these cases even-order slow-roll parameters approach non-negligible constants while the odd ones are asymptotically vanishing in the quasi-de Sitter regime

Inhibition of NF-κB activity in the hypothalamic paraventricular nucleus attenuates hypertension and cardiac hypertrophy by modulating cytokines and attenuating oxidative stress

Energy Technology Data Exchange (ETDEWEB)

Yu, Xiao-Jing [Department of Physiology and Pathophysiology, Xi' an Jiaotong University School of Basic Medical Sciences, Xi' an Jiaotong University Cardiovascular Research Center, Xi' an Jiaotong University Health Science Center, Xi' an 710061 (China); Zhang, Dong-Mei [Department of Physiology, Dalian Medical University, Dalian 116044 (China); Jia, Lin-Lin; Qi, Jie; Song, Xin-Ai; Tan, Hong [Department of Physiology and Pathophysiology, Xi' an Jiaotong University School of Basic Medical Sciences, Xi' an Jiaotong University Cardiovascular Research Center, Xi' an Jiaotong University Health Science Center, Xi' an 710061 (China); Cui, Wei [Department of Endocrinology and Metabolism, First Affiliated Hospital of Xi' an Jiaotong University, Xi' an Jiaotong University Health Science Center, Xi' an 710061 (China); Chen, Wensheng [Department of Cardiovascular Surgery, Xijing Hospital, Fourth Military Medical University, Xi' an 710032 (China); Zhu, Guo-Qing [Key Laboratory of Cardiovascular Disease and Molecular Intervention, Department of Physiology, Nanjing Medical University, Nanjing 210029 (China); Qin, Da-Nian, E-mail: dnqin@stu.edu.cn [Department of Physiology, Shantou University Medical College, Shantou 515041 (China); Kang, Yu-Ming, E-mail: ykang@mail.xjtu.edu.cn [Department of Physiology and Pathophysiology, Xi' an Jiaotong University School of Basic Medical Sciences, Xi' an Jiaotong University Cardiovascular Research Center, Xi' an Jiaotong University Health Science Center, Xi' an 710061 (China)

2015-05-01

We hypothesized that chronic inhibition of NF-κB activity in the hypothalamic paraventricular nucleus (PVN) delays the progression of hypertension and attenuates cardiac hypertrophy by up-regulating anti-inflammatory cytokines, reducing pro-inflammatory cytokines (PICs), attenuating nuclear factor-κB (NF-κB) p65 and NAD(P)H oxidase in the PVN of young spontaneously hypertensive rats (SHR). Young normotensive Wistar–Kyoto (WKY) and SHR rats received bilateral PVN infusions with NF–κB inhibitor pyrrolidine dithiocarbamate (PDTC) or vehicle for 4 weeks. SHR rats had higher mean arterial pressure and cardiac hypertrophy as indicated by increased whole heart weight/body weight ratio, whole heart weight/tibia length ratio, left ventricular weight/tibia length ratio, cardiomyocyte diameters of the left cardiac ventricle, and mRNA expressions of cardiac atrial natriuretic peptide (ANP) and beta-myosin heavy chain (β-MHC). These SHR rats had higher PVN levels of proinflammatory cytokines (PICs), reactive oxygen species (ROS), the chemokine monocyte chemoattractant protein-1 (MCP-1), NAD(P)H oxidase activity, mRNA expression of NOX-2 and NOX-4, and lower PVN IL-10, and higher plasma levels of PICs and NE, and lower plasma IL-10. PVN infusion of NF-κB inhibitor PDTC attenuated all these changes. These findings suggest that NF-κB activation in the PVN increases sympathoexcitation and hypertensive response, which are associated with the increases of PICs and oxidative stress in the PVN; PVN inhibition of NF-κB activity attenuates PICs and oxidative stress in the PVN, thereby attenuates hypertension and cardiac hypertrophy. - Highlights: • Spontaneously hypertensive rats exhibit neurohormonal excitation in the PVN. • PVN inhibition of NF-κB attenuates hypertension-induced cardiac hypertrophy. • PVN inhibition of NF-κB attenuates hypertension-induced neurohormonal excitation. • PVN inhibition of NF-κB attenuates hypertension-induced imbalance of cytokines

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

Note: Determination of torsional spring constant of atomic force microscopy cantilevers: Combining normal spring constant and classical beam theory

DEFF Research Database (Denmark)

Álvarez-Asencio, R.; Thormann, Esben; Rutland, M.W.

2013-01-01

A technique has been developed for the calculation of torsional spring constants for AFM cantilevers based on the combination of the normal spring constant and plate/beam theory. It is easy to apply and allow the determination of torsional constants for stiff cantilevers where the thermal power s...... spectrum is difficult to obtain due to the high resonance frequency and low signal/noise ratio. The applicability is shown to be general and this simple approach can thus be used to obtain torsional constants for any beam shaped cantilever. © 2013 AIP Publishing LLC....

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.

Patient position alters attenuation effects in multipinhole cardiac SPECT.

Science.gov (United States)

Timmins, Rachel; Ruddy, Terrence D; Wells, R Glenn

2015-03-01

Dedicated cardiac cameras offer improved sensitivity over conventional SPECT cameras. Sensitivity gains are obtained by large numbers of detectors and novel collimator arrangements such as an array of multiple pinholes that focus on the heart. Pinholes lead to variable amounts of attenuation as a source is moved within the camera field of view. This study evaluated the effects of this variable attenuation on myocardial SPECT images. Computer simulations were performed for a set of nine point sources distributed in the left ventricular wall (LV). Sources were placed at the location of the heart in both an anthropomorphic and a water-cylinder computer phantom. Sources were translated in x, y, and z by up to 5 cm from the center. Projections were simulated with and without attenuation and the changes in attenuation were compared. A LV with an inferior wall defect was also simulated in both phantoms over the same range of positions. Real camera data were acquired on a Discovery NM530c camera (GE Healthcare, Haifa, Israel) for five min in list-mode using an anthropomorphic phantom (DataSpectrum, Durham, NC) with 100 MBq of Tc-99m in the LV. Images were taken over the same range of positions as the simulations and were compared based on the summed perfusion score (SPS), defect width, and apparent defect uptake for each position. Point sources in the water phantom showed absolute changes in attenuation of ≤8% over the range of positions and relative changes of ≤5% compared to the apex. In the anthropomorphic computer simulations, absolute change increased to 20%. The changes in relative attenuation caused a change in SPS of position-dependent changes were removed with attenuation correction. Translation of a source relative to a multipinhole camera caused only small changes in homogeneous phantoms with SPS changing position-dependent changes in attenuation.

An Approximate Method for the Acoustic Attenuating VTI Eikonal Equation

KAUST Repository

Hao, Q.

2017-05-26

We present an approximate method to solve the acoustic eikonal equation for attenuating transversely isotropic media with a vertical symmetry axis (VTI). A perturbation method is used to derive the perturbation formula for complex-valued traveltimes. The application of Shanks transform further enhances the accuracy of approximation. We derive both analytical and numerical solutions to the acoustic eikonal equation. The analytic solution is valid for homogeneous VTI media with moderate anellipticity and strong attenuation and attenuation-anisotropy. The numerical solution is applicable for inhomogeneous attenuating VTI media.

An Approximate Method for the Acoustic Attenuating VTI Eikonal Equation

KAUST Repository

Hao, Q.; Alkhalifah, Tariq Ali

2017-01-01

We present an approximate method to solve the acoustic eikonal equation for attenuating transversely isotropic media with a vertical symmetry axis (VTI). A perturbation method is used to derive the perturbation formula for complex-valued traveltimes. The application of Shanks transform further enhances the accuracy of approximation. We derive both analytical and numerical solutions to the acoustic eikonal equation. The analytic solution is valid for homogeneous VTI media with moderate anellipticity and strong attenuation and attenuation-anisotropy. The numerical solution is applicable for inhomogeneous attenuating VTI media.

When and Why Mimicry is Facilitated and Attenuated

NARCIS (Netherlands)

Stel, Mariëlle; van Dijk, Eric; van Baaren, Rick B.

2016-01-01

Although people tend to mimic others automatically, mimicry is facilitated or attenuated depending on the specific context. In the current paper, the authors discuss when mimicry is facilitated and attenuated depending on characteristics of situations, targets, and observers. On the basis of the

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

Electromagnetic Wave Attenuation in Atmospheric Pressure Plasma

International Nuclear Information System (INIS)

Zhang Shu; Hu Xiwei; Liu Minghai; Luo Fang; Feng Zelong

2007-01-01

When an electromagnetic (EM) wave propagates in an atmospheric pressure plasma (APP) layer, its attenuation depends on the APP parameters such as the layer width, the electron density and its profile and collision frequency between electrons and neutrals. This paper proposes that a combined parameter-the product of the line average electron density n-bar and width d of the APP layer (i.e., the total number of electrons in a unit volume along the wave propagation path) can play a more explicit and decisive role in the wave attenuation than any of the above individual parameters does. The attenuation of the EM wave via the product of n-bar and d with various collision frequencies between electrons and neutrals is presented

Experimental Determination of the Avogadro Constant

Indian Academy of Sciences (India)

mental physical constant such as charge of an electron or the. Boltzmann constant ... ideas was that the number of particles or molecules in a gas of given volume could not ... knowledge of at least one property of a single molecule. Loschmidt ...

Investigation of multilayered nanocomposites as low energy X-Rays attenuators

Energy Technology Data Exchange (ETDEWEB)

Silva, Liliane; Batista, Adriana S.M.; Nascimento, Jefferson P.; Furtado, Clascídia A.; Faria, Luiz O., E-mail: asfisica@gmail.com, E-mail: adriananuclear@yahoo.com.br, E-mail: farialo@cdtn.br, E-mail: nascimentopatricio@yahoo.com.br, E-mail: clas@cdtn.br [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil); Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

2017-11-01

The development of radiation attenuating materials has application in radioprotection and conditioning of short-lived waste. Polymeric materials can serve as a matrix for the dispersion of nanomaterials with good attenuation features, resulting in lightweight, conformable, flexible and easy-to-process materials. Thus, some well-known shielding materials could be used in low proportion for the formation of new materials. On the other hand, nanostructured carbon materials, such as graphene oxide (GO) and carbon nanotubes (NTCs), have been reported recently to show enhanced attenuation properties. In this sense, polymeric matrixes provide the necessary flexibility for use in various applications that require molding. For the present work, poly(vinylidene fluoride) [PVDF] homopolymers and its fluorinated copolymers were filled with nanosized metallic and graphene oxides in order to produce nanocomposites with increased low energy X-ray attenuation efficiency. Film samples of PVDF/reduced Graphene Oxide [PVDF/rGO] and Poly(vinylidene fluoride – tryfluorethylene)/Barium Oxide [P(VDF-TrFE)/BaO] were synthesized. In a second step, the samples were then sandwiched between Kapton® layers and exposed to X-rays source (8.5 keV). The samples were characterized with Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The attenuation coefficient was evaluated and compared with the attenuation of the individual constituents. It was observed an increase in the linear attenuation coefficient of the layered materials, justifying further investigation of these nanostructured composites as X-ray or gamma radiation attenuators. (author)

Investigation of multilayered nanocomposites as low energy X-Rays attenuators

International Nuclear Information System (INIS)

Silva, Liliane; Batista, Adriana S.M.; Nascimento, Jefferson P.; Furtado, Clascídia A.; Faria, Luiz O.

2017-01-01

The development of radiation attenuating materials has application in radioprotection and conditioning of short-lived waste. Polymeric materials can serve as a matrix for the dispersion of nanomaterials with good attenuation features, resulting in lightweight, conformable, flexible and easy-to-process materials. Thus, some well-known shielding materials could be used in low proportion for the formation of new materials. On the other hand, nanostructured carbon materials, such as graphene oxide (GO) and carbon nanotubes (NTCs), have been reported recently to show enhanced attenuation properties. In this sense, polymeric matrixes provide the necessary flexibility for use in various applications that require molding. For the present work, poly(vinylidene fluoride) [PVDF] homopolymers and its fluorinated copolymers were filled with nanosized metallic and graphene oxides in order to produce nanocomposites with increased low energy X-ray attenuation efficiency. Film samples of PVDF/reduced Graphene Oxide [PVDF/rGO] and Poly(vinylidene fluoride – tryfluorethylene)/Barium Oxide [P(VDF-TrFE)/BaO] were synthesized. In a second step, the samples were then sandwiched between Kapton® layers and exposed to X-rays source (8.5 keV). The samples were characterized with Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The attenuation coefficient was evaluated and compared with the attenuation of the individual constituents. It was observed an increase in the linear attenuation coefficient of the layered materials, justifying further investigation of these nanostructured composites as X-ray or gamma radiation attenuators. (author)

Wormholes and the cosmological constant problem.

Science.gov (United States)

Klebanov, I.

The author reviews the cosmological constant problem and the recently proposed wormhole mechanism for its solution. Summation over wormholes in the Euclidean path integral for gravity turns all the coupling parameters into dynamical variables, sampled from a probability distribution. A formal saddle point analysis results in a distribution with a sharp peak at the cosmological constant equal to zero, which appears to solve the cosmological constant problem. He discusses the instabilities of the gravitational Euclidean path integral and the difficulties with its interpretation. He presents an alternate formalism for baby universes, based on the "third quantization" of the Wheeler-De Witt equation. This approach is analyzed in a minisuperspace model for quantum gravity, where it reduces to simple quantum mechanics. Once again, the coupling parameters become dynamical. Unfortunately, the a priori probability distribution for the cosmological constant and other parameters is typically a smooth function, with no sharp peaks.

The cosmological constant in theories with finite spacetime

International Nuclear Information System (INIS)

Kummer, Janis

2014-08-01

We study the role of the cosmological constant in different theories with finite spacetime. The cosmological constant appears both as an initial condition and as a constant of integration. In the context of the cosmological constant problem a new model will be presented. This modification of general relativity generates a small, non-vanishing cosmological constant, which is radiatively stable. The dynamics of the expansion of the universe in this model will be analyzed. Eventually, we try to solve the emergent problems concerning the generation of accelerated expansion using a quintessence model of dark energy.

The Hubble Constant

Directory of Open Access Journals (Sweden)

Neal Jackson

2015-09-01

Full Text Available I review the current state of determinations of the Hubble constant, which gives the length scale of the Universe by relating the expansion velocity of objects to their distance. There are two broad categories of measurements. The first uses individual astrophysical objects which have some property that allows their intrinsic luminosity or size to be determined, or allows the determination of their distance by geometric means. The second category comprises the use of all-sky cosmic microwave background, or correlations between large samples of galaxies, to determine information about the geometry of the Universe and hence the Hubble constant, typically in a combination with other cosmological parameters. Many, but not all, object-based measurements give H_0 values of around 72–74 km s^–1 Mpc^–1, with typical errors of 2–3 km s^–1 Mpc^–1. This is in mild discrepancy with CMB-based measurements, in particular those from the Planck satellite, which give values of 67–68 km s^–1 Mpc^–1 and typical errors of 1–2 km s^–1 Mpc^–1. The size of the remaining systematics indicate that accuracy rather than precision is the remaining problem in a good determination of the Hubble constant. Whether a discrepancy exists, and whether new physics is needed to resolve it, depends on details of the systematics of the object-based methods, and also on the assumptions about other cosmological parameters and which datasets are combined in the case of the all-sky methods.

On the attenuation of the ambient seismic field

International Nuclear Information System (INIS)

Weemstra, C.

2013-01-01

Although myriad applications exploiting the ambient seismic field have been reported to date, comparatively little attention has been paid to its potential to resolve subsurface attenuation. The ambient seismic field, however, may ultimately prove itself an invaluable asset in constraining subsurface attenuation structure. Especially areas with dense seismometer coverage hold great potential. Moreover, since this coverage continues to grow, significant developments may await in the future. Subsurface structure in terms of attenuation is of great importance for many reasons. For example, knowledge of the attenuation structure may aid in predicting ground motions caused by future large earthquakes. From a scientific perspective, a great deal of new information may be extracted, potentially fostering research in related fields (e.g., geodynamics, hydrology). Both from an environmental and economic point of view, inversion of the ambient seismic wavefield for attenuation structure may in the future provide a means to image hydrocarbon reservoirs. In sufficiently diffuse wavefields, simple cross-correlation of long noise time series recorded by two receivers results in the response at one of the receivers as if there was a source at the position of the other. I present a case study that shows that thus retrieved surface waves can be used to recover attenuation beneath an array of ocean-bottom seismometers. Given the small aperture of the seismic survey, this is unprecedented. Unambiguous interpretation of recovered attenuation values is of major importance. Lack of understanding of the effect that preprocessing has on the amplitude of the noise cross-correlation prevents such unambiguous interpretation. I carefully examine the effect spectral whitening has on the noise cross-correlation. Emphasis is given to the dependence of the amplitudes on the length of the time windows employed in the cross-correlation procedure. Short time-window lengths may require an additional

Patient position alters attenuation effects in multipinhole cardiac SPECT

International Nuclear Information System (INIS)

Timmins, Rachel; Ruddy, Terrence D.; Wells, R. Glenn

2015-01-01

Purpose: Dedicated cardiac cameras offer improved sensitivity over conventional SPECT cameras. Sensitivity gains are obtained by large numbers of detectors and novel collimator arrangements such as an array of multiple pinholes that focus on the heart. Pinholes lead to variable amounts of attenuation as a source is moved within the camera field of view. This study evaluated the effects of this variable attenuation on myocardial SPECT images. Methods: Computer simulations were performed for a set of nine point sources distributed in the left ventricular wall (LV). Sources were placed at the location of the heart in both an anthropomorphic and a water-cylinder computer phantom. Sources were translated in x, y, and z by up to 5 cm from the center. Projections were simulated with and without attenuation and the changes in attenuation were compared. A LV with an inferior wall defect was also simulated in both phantoms over the same range of positions. Real camera data were acquired on a Discovery NM530c camera (GE Healthcare, Haifa, Israel) for five min in list-mode using an anthropomorphic phantom (DataSpectrum, Durham, NC) with 100 MBq of Tc-99m in the LV. Images were taken over the same range of positions as the simulations and were compared based on the summed perfusion score (SPS), defect width, and apparent defect uptake for each position. Results: Point sources in the water phantom showed absolute changes in attenuation of ≤8% over the range of positions and relative changes of ≤5% compared to the apex. In the anthropomorphic computer simulations, absolute change increased to 20%. The changes in relative attenuation caused a change in SPS of <1.5 for the water phantom but up to 4.2 in the anthropomorphic phantom. Changes were larger for axial than for transverse translations. These results were supported by SPS changes of up to six seen in the physical anthropomorphic phantom for axial translations. Defect width was also seen to significantly increase. The

An Analytical-empirical Calculation of Linear Attenuation Coefficient of Megavoltage Photon Beams.

Science.gov (United States)

Seif, F; Tahmasebi-Birgani, M J; Bayatiani, M R

2017-09-01

In this study, a method for linear attenuation coefficient calculation was introduced. Linear attenuation coefficient was calculated with a new method that base on the physics of interaction of photon with matter, mathematical calculation and x-ray spectrum consideration. The calculation was done for Cerrobend as a common radiotherapy modifier and Mercury. The values of calculated linear attenuation coefficient with this new method are in acceptable range. Also, the linear attenuation coefficient decreases slightly as the thickness of attenuating filter (Cerrobend or mercury) increased, so the procedure of linear attenuation coefficient variation is in agreement with other documents. The results showed that the attenuation ability of mercury was about 1.44 times more than Cerrobend. The method that was introduced in this study for linear attenuation coefficient calculation is general enough to treat beam modifiers with any shape or material by using the same formalism; however, calculating was made only for mercury and Cerrobend attenuator. On the other hand, it seems that this method is suitable for high energy shields or protector designing.

Constant-roll (quasi-)linear inflation

Science.gov (United States)

Karam, A.; Marzola, L.; Pappas, T.; Racioppi, A.; Tamvakis, K.

2018-05-01

In constant-roll inflation, the scalar field that drives the accelerated expansion of the Universe is rolling down its potential at a constant rate. Within this framework, we highlight the relations between the Hubble slow-roll parameters and the potential ones, studying in detail the case of a single-field Coleman-Weinberg model characterised by a non-minimal coupling of the inflaton to gravity. With respect to the exact constant-roll predictions, we find that assuming an approximate slow-roll behaviour yields a difference of Δ r = 0.001 in the tensor-to-scalar ratio prediction. Such a discrepancy is in principle testable by future satellite missions. As for the scalar spectral index ns, we find that the existing 2-σ bound constrains the value of the non-minimal coupling to ξphi ~ 0.29–0.31 in the model under consideration.

The Yamabe constant

International Nuclear Information System (INIS)

O Murchadha, N.

1991-01-01

The set of riemannian three-metrics with positive Yamabe constant defines the space of independent data for the gravitational field. The boundary of this set is investigated, and it is shown that metrics close to the boundary satisfy the positive-energy theorem. (Author) 18 refs

MNAtoolbox: A Monitored Natural Attenuation Site Screening Program

Energy Technology Data Exchange (ETDEWEB)

Borns, David J.; Brady, Patrick V.; Brady, Warren D.; Krupka, Kenneth M.; Spalding, Brian P.; Waters, Robert D.; Zhang, Pengchu

1999-07-12

Screening of sites for the potential application and reliance upon monitored natural attenuation (MNA) can be done using MNAtoolbox, a web-based tool for estimating extent of biodegradation, chemical transformation, and dilution. MNAtoolbox uses site-specific input data, where available (default parameters are taken from the literature), to roughly quantify the nature and extent of attenuation at a particular site. Use of MNAtoolbox provides 3 important elements of site evaluation: (1) Identifies likely attenuation pathways, (2) Clearly identifies sites where MNA is inappropriate, and (3) Evaluates data requirements for subsequent reliance on MNA as a sole or partial corrective action.

Charge dependence of the pion-nucleon coupling constant

Directory of Open Access Journals (Sweden)

V. A. Babenko

2015-07-01

Full Text Available On the basis of the Yukawa potential we study the pion-nucleon coupling constants for the neutral and charged pions assuming that nuclear forces at low energies are mainly determined by the exchange of virtual pions. We obtain the charged pseudovector pion-nucleon coupling constant f2π± = 0.0804(7 by making the use of experimental low-energy scattering parameters for the singlet pp- and np-scattering, and also by use of the neutral pseudovector pion-nucleon coupling constant f2π0 = 0.0749(7. Corresponding value of the charged pseudoscalar pion-nucleon coupling constant g2π0 / 4π = 14.55(13 is also determined. This calculated value of the charged pseudoscalar pion-nucleon coupling constant is in fully agreement with the experimental constant g2π0 / 4π = 14.52(26 obtained by the Uppsala Neutron Research Group. Our results show considerable charge splitting of the pion-nucleon coupling constant.

A quadri-constant fraction discriminator

International Nuclear Information System (INIS)

Wang Wei; Gu Zhongdao

1992-01-01

A quad Constant Fraction (Amplitude and Rise Time Compensation) Discriminator Circuit is described, which is based on the ECL high-speed dual comparator AD 9687. The CFD (ARCD) is of the constant fraction timing type (the amplitude and rise time compensation timing type) employing a leading edge discriminator to eliminate error triggers caused by noises. A timing walk measurement indicates a timing walk of less than +- 150 ps from -50 mV to -5 V

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.

On special relativity with cosmological constant

International Nuclear Information System (INIS)

Guo Hanying; Huang Chaoguang; Xu Zhan; Zhou Bin

2004-01-01

Based on the principle of relativity and the postulate of invariant speed and length, we propose the theory of special relativity with cosmological constant SRc,R, in which the cosmological constant is linked with the invariant length. Its relation with the doubly special relativity is briefly mentioned

Attenuation of Reactor Gamma Radiation and Fast Neutrons Through Large Single-Crystal Materials

International Nuclear Information System (INIS)

Adib, M.

2009-01-01

A generalized formula is given which, for neutron energies in the range 10-4< E< 10 eV and gamma rays with average energy 2 MeV , permits calculation of the transmission properties of several single crystal materials important for neutron scattering instrumentation. A computer program Filter was developed which permits the calculation of attenuation of gamma radiation, nuclear capture, thermal diffuse and Bragg-scattering cross-sections as a function of materials constants, temperature and neutron energy. The applicability of the deduced formula along with the code checked from the obtained agreement between the calculated and experimental neutron transmission through various single-crystals A feasibility study for use of Si, Ge, Pb, Bi and sapphire is detailed in terms of optimum crystal thickness, mosaic spread and cutting plane for efficient transmission of thermal reactor neutrons and for rejection of the accompanying fast neutrons and gamma rays.

Characterizing the attenuation of coaxial and rectangular microwave-frequency waveguides at cryogenic temperatures

Energy Technology Data Exchange (ETDEWEB)

Kurpiers, Philipp; Walter, Theodore; Magnard, Paul; Salathe, Yves; Wallraff, Andreas [ETH Zuerich, Department of Physics, Zuerich (Switzerland)

2017-12-15

Low-loss waveguides are required for quantum communication at distances beyond the chip-scale for any low-temperature solid-state implementation of quantum information processors. We measure and analyze the attenuation constant of commercially available microwave-frequency waveguides down to millikelvin temperatures and single photon levels. More specifically, we characterize the frequency-dependent loss of a range of coaxial and rectangular microwave waveguides down to 0.005 dB/m using a resonant-cavity technique. We study the loss tangent and relative permittivity of commonly used dielectric waveguide materials by measurements of the internal quality factors and their comparison with established loss models. The results of our characterization are relevant for accurately predicting the signal levels at the input of cryogenic devices, for reducing the loss in any detection chain, and for estimating the heat load induced by signal dissipation in cryogenic systems. (orig.)

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

Reliability concerns with logical constants in Xilinx FPGA designs

Energy Technology Data Exchange (ETDEWEB)

Quinn, Heather M [Los Alamos National Laboratory; Graham, Paul [Los Alamos National Laboratory; Morgan, Keith [Los Alamos National Laboratory; Ostler, Patrick [Los Alamos National Laboratory; Allen, Greg [JPL; Swift, Gary [XILINX; Tseng, Chen W [XILINX

2009-01-01

In Xilinx Field Programmable Gate Arrays logical constants, which ground unused inputs and provide constants for designs, are implemented in SEU-susceptible logic. In the past, these logical constants have been shown to cause the user circuit to output bad data and were not resetable through off-line rcconfiguration. In the more recent devices, logical constants are less problematic, though mitigation should still be considered for high reliability applications. In conclusion, we have presented a number of reliability concerns with logical constants in the Xilinx Virtex family. There are two main categories of logical constants: implicit and explicit logical constants. In all of the Virtex devices, the implicit logical constants are implemented using half latches, which in the most recent devices are several orders of magnitudes smaller than configuration bit cells. Explicit logical constants are implemented exclusively using constant LUTs in the Virtex-I and Virtex-II, and use a combination of constant LUTs and architectural posts to the ground plane in the Virtex-4. We have also presented mitigation methods and options for these devices. While SEUs in implicit and some types of explicit logical constants can cause data corrupt, the chance of failure from these components is now much smaller than it was in the Virtex-I device. Therefore, for many cases, mitigation might not be necessary, except under extremely high reliability situations.

Fine-structure constant: Is it really a constant

International Nuclear Information System (INIS)

Bekenstein, J.D.

1982-01-01

It is often claimed that the fine-structure ''constant'' α is shown to be strictly constant in time by a variety of astronomical and geophysical results. These constrain its fractional rate of change alpha-dot/α to at least some orders of magnitude below the Hubble rate H 0 . We argue that the conclusion is not as straightforward as claimed since there are good physical reasons to expect alpha-dot/α 0 . We propose to decide the issue by constructing a framework for a variability based on very general assumptions: covariance, gauge invariance, causality, and time-reversal invariance of electromagnetism, as well as the idea that the Planck-Wheeler length (10 -33 cm) is the shortest scale allowable in any theory. The framework endows α with well-defined dynamics, and entails a modification of Maxwell electrodynamics. It proves very difficult to rule it out with purely electromagnetic experiments. In a cosmological setting, the framework predicts an alpha-dot/α which can be compatible with the astronomical constraints; hence, these are too insensitive to rule out α variability. There is marginal conflict with the geophysical constraints: however, no firm decision is possible because of uncertainty about various cosmological parameters. By contrast the framework's predictions for spatial gradients of α are in fatal conflict with the results of the Eoetvoes-Dicke-Braginsky experiments. Hence these tests of the equivalence principle rule out with confidence spacetime variability of α at any level

Weak Acid Ionization Constants and the Determination of Weak Acid-Weak Base Reaction Equilibrium Constants in the General Chemistry Laboratory

Science.gov (United States)

Nyasulu, Frazier; McMills, Lauren; Barlag, Rebecca

2013-01-01

A laboratory to determine the equilibrium constants of weak acid negative weak base reactions is described. The equilibrium constants of component reactions when multiplied together equal the numerical value of the equilibrium constant of the summative reaction. The component reactions are weak acid ionization reactions, weak base hydrolysis…

Production in constant evolution

International Nuclear Information System (INIS)

Lozano, T.

2009-01-01

The Cofrentes Nuclear Power Plant now has 25 years of operation behind it: a quarter century adding value and demonstrating the reasons why it is one of the most important energy producing facilities in the Spanish power market. Particularly noteworthy is the enterprising spirit of the plant, which has strived to continuously improve with the large number of modernization projects that it has undertaken over the past 25 years. The plant has constantly evolved thanks to the amount of investments made to improve safety and reliability and the perseverance to stay technologically up to date. Efficiency, training and teamwork have been key to the success of the plant over these 25 years of constant change and progress. (Author)

Scalar-tensor cosmology with cosmological constant

International Nuclear Information System (INIS)

Maslanka, K.

1983-01-01

The equations of scalar-tensor theory of gravitation with cosmological constant in the case of homogeneous and isotropic cosmological model can be reduced to dynamical system of three differential equations with unknown functions H=R/R, THETA=phi/phi, S=e/phi. When new variables are introduced the system becomes more symmetrical and cosmological solutions R(t), phi(t), e(t) are found. It is shown that when cosmological constant is introduced large class of solutions which depend also on Dicke-Brans parameter can be obtained. Investigations of these solutions give general limits for cosmological constant and mean density of matter in plane model. (author)

Effects of Constant Flow vs. Constant Pressure Perfusion on Fluid Filtration in Severe Hypothermic Isolated Blood-Perfused Rat Lungs.

Science.gov (United States)

Halsøy, Kathrine; Kondratiev, Timofey; Tveita, Torkjel; Bjertnaes, Lars J

2016-01-01

Victims of severe accidental hypothermia are prone to fluid extravasation but rarely develop lung edema. We hypothesize that combined hypothermia-induced increase in pulmonary vascular resistance (PVR) and a concomitant fall in cardiac output protect the lungs against edema development. Our aim was to explore in hypothermic-isolated blood-perfused rat lungs whether perfusion at constant pressure influences fluid filtration differently from perfusion at constant flow. Isolated blood-perfused rat lungs were hanging freely in a weight transducer for measuring weight changes (ΔW). Fluid filtration coefficient (Kfc), was determined by transiently elevating left atrial pressure (Pla) by 5.8 mmHg two times each during normothermia (37°C) and during hypothermia (15°C). The lung preparations were randomized to two groups. One group was perfused with constant flow (Constant flow group) and the other group with constant pulmonary artery pressure (Constant PPA group). Microvascular pressure (Pmv) was determined before and during elevation of Pla (ΔPmv) by means of the double occlusion technique. Kfc was calculated with the formula Kfc = ΔW/ΔPmv/min. All Kfc values were normalized to predicted lung weight (P LW ), which was based on body weight (BW) according to the formula: P LW  = 0.0053 BW - 0.48 and presented as Kfc PLW in mg/min/mmHg/g. At cessation, bronchoalveolar lavage (BAL) fluid/perfusate protein concentration (B/P) ratio was determined photometrically. Data were analyzed with parametric or non-parametric tests as appropriate. p  Kfc PLW and B/P ratio increased significantly by more than 10-fold during hypothermia concerted by visible signs of edema in the trachea. Hemoglobin and hematocrit increased within the Constant flow group and between the groups at cessation of the experiments. In hypothermic rat lungs perfused at constant flow, fluid filtration coefficient per gram P LW and B/P ratio increased more than 10-fold concerted by increased

Shapley Value for Constant-sum Games

NARCIS (Netherlands)

Khmelnitskaya, A.B.

2002-01-01

It is proved that Young's axiomatization for the Shapley value by marginalism, efficiency, and symmetry is still valid for the Shapley value defined on the class of nonnegative constant-sum games and on the entire class of constant-sum games as well. To support an interest to study the class of

The use of microperforated plates to attenuate cavity resonances

DEFF Research Database (Denmark)

Fenech, Benjamin; Keith, Graeme; Jacobsen, Finn

2006-01-01

The use of microperforated plates to introduce damping in a closed cavity is examined. By placing a microperforated plate well inside the cavity instead of near a wall as traditionally done in room acoustics, high attenuation can be obtained for specific acoustic modes, compared with the lower...... attenuation that can be obtained in a broad frequency range with the conventional position of the plate. An analytical method for predicting the attenuation is presented. The method involves finding complex eigenvalues and eigenfunctions for the modified cavity and makes it possible to predict Green......'s functions. The results, which are validated experimentally, show that a microperforated plate can provide substantial attenuation of modes in a cavity. One possible application of these findings is the treatment of boiler tones in heat-exchanger cavities....

Evaluation of elastic constants of materials using the frequency spectrum

International Nuclear Information System (INIS)

Silva Neto, Ramiro J. da; Baroni, Douglas B.; Bittencourt, Marcelo de S.Q.

2015-01-01

The characterization of materials made with the support of non-destructive techniques has great importance in industrial applications. The ultrasonic techniques are distinguished by good resolution to measure small variations of wave velocities as a result of changes in the character suffered by a particular material. In general these ultrasonic techniques are studied in the time domain, which represents an experimental difficulties when thin materials are analyzed, as well as to attenuate the ultrasonic signal drastically. An ultrasonic technique that uses the frequency domain is used in this study aiming to provide good time measurements to calculate the elastic constants of the first order in an aluminum alloy 6351. With the aid of a statistical approach was possible to have good results of tests performed when compared by a time domain technique already well explored in Ultrasound works produced in the Nuclear Engineering Institute Laboratory (LABUS / IEN) and also presented in most of the package, in good agreement with the theoretical model established in literature and used to validate the experiment, which was found in the results with good approximation. The relevance of this work in the nuclear area is associated with the interest to know the mechanical properties of structural components of the nuclear industry, which is currently studied as a rule, resorting to the computer simulations or previously during the operation of the system. (author)

Evaluation of elastic constants of materials using the frequency spectrum

Energy Technology Data Exchange (ETDEWEB)

Silva Neto, Ramiro J. da; Baroni, Douglas B.; Bittencourt, Marcelo de S.Q., E-mail: ramirobd@gmail.com [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Departamento de Materiais Nucleares. Laboratorio de Ultrassom

2015-07-01

The characterization of materials made with the support of non-destructive techniques has great importance in industrial applications. The ultrasonic techniques are distinguished by good resolution to measure small variations of wave velocities as a result of changes in the character suffered by a particular material. In general these ultrasonic techniques are studied in the time domain, which represents an experimental difficulties when thin materials are analyzed, as well as to attenuate the ultrasonic signal drastically. An ultrasonic technique that uses the frequency domain is used in this study aiming to provide good time measurements to calculate the elastic constants of the first order in an aluminum alloy 6351. With the aid of a statistical approach was possible to have good results of tests performed when compared by a time domain technique already well explored in Ultrasound works produced in the Nuclear Engineering Institute Laboratory (LABUS / IEN) and also presented in most of the package, in good agreement with the theoretical model established in literature and used to validate the experiment, which was found in the results with good approximation. The relevance of this work in the nuclear area is associated with the interest to know the mechanical properties of structural components of the nuclear industry, which is currently studied as a rule, resorting to the computer simulations or previously during the operation of the system. (author)

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...

Fundamental Constants in Physics and their Time Dependence

CERN Multimedia

CERN. Geneva

2008-01-01

In the Standard Model of Particle Physics we are dealing with 28 fundamental constants. In the experiments these constants can be measured, but theoretically they are not understood. I will discuss these constants, which are mostly mass parameters. Astrophysical measurements indicate that the finestructure constant is not a real constant, but depends on time. Grand unification then implies also a time variation of the QCD scale. Thus the masses of the atomic nuclei and the magnetic moments of the nuclei will depend on time. I proposed an experiment, which is currently done by Prof. Haensch in Munich and his group. The first results indicate a time dependence of the QCD scale. I will discuss the theoretical implications.

Elastic constants of diamond from molecular dynamics simulations

International Nuclear Information System (INIS)

Gao Guangtu; Van Workum, Kevin; Schall, J David; Harrison, Judith A

2006-01-01

The elastic constants of diamond between 100 and 1100 K have been calculated for the first time using molecular dynamics and the second-generation, reactive empirical bond-order potential (REBO). This version of the REBO potential was used because it was redesigned to be able to model the elastic properties of diamond and graphite at 0 K while maintaining its original capabilities. The independent elastic constants of diamond, C 11 , C 12 , and C 44 , and the bulk modulus were all calculated as a function of temperature, and the results from the three different methods are in excellent agreement. By extrapolating the elastic constant data to 0 K, it is clear that the values obtained here agree with the previously calculated 0 K elastic constants. Because the second-generation REBO potential was fit to obtain better solid-state force constants for diamond and graphite, the agreement with the 0 K elastic constants is not surprising. In addition, the functional form of the second-generation REBO potential is able to qualitatively model the functional dependence of the elastic constants and bulk modulus of diamond at non-zero temperatures. In contrast, reactive potentials based on other functional forms do not reproduce the correct temperature dependence of the elastic constants. The second-generation REBO potential also correctly predicts that diamond has a negative Cauchy pressure in the temperature range examined

Cosmological constant problem

International Nuclear Information System (INIS)

Weinberg, S.

1989-01-01

Cosmological constant problem is discussed. History of the problem is briefly considered. Five different approaches to solution of the problem are described: supersymmetry, supergravity, superstring; anthropic approach; mechamism of lagrangian alignment; modification of gravitation theory and quantum cosmology. It is noted that approach, based on quantum cosmology is the most promising one

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)

Dose rate constants for new dose quantities

International Nuclear Information System (INIS)

Tschurlovits, M.; Daverda, G.; Leitner, A.

1992-01-01

Conceptual changes and new quantities made is necessary to reassess dose rate quantities. Calculations of the dose rate constant were done for air kerma, ambient dose equivalent and directional dose equivalent. The number of radionuclides is more than 200. The threshold energy is selected as 20 keV for the dose equivalent constants. The dose rate constant for the photon equivalent dose as used mainly in German speaking countries as a temporary quantity is also included. (Author)

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.

Garbage-free reversible constant multipliers for arbitrary integers

DEFF Research Database (Denmark)

Mogensen, Torben Ægidius

2013-01-01

We present a method for constructing reversible circuitry for multiplying integers by arbitrary integer constants. The method is based on Mealy machines and gives circuits whose size are (in the worst case) linear in the size of the constant. This makes the method unsuitable for large constants...

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.

Practical method of breast attenuation correction for cardiac SPECT

International Nuclear Information System (INIS)

Oliveira, Anderson de; Nogueira, Tindyua; Gutterres, Ricardo Fraga; Megueriam, Berdj Aram; Santos, Goncalo Rodrigues dos

2007-01-01

The breast attenuation effects on SPECT (Single Photon Emission Tomography) myocardium perfusion procedures have been lately scope of continuous inquiry. The requested attenuation correction factors are usually achieved by transmission analysis, making up the exposure of a standard external source to the SPECT, as a routine step. However, its high cost makes this methodology not fully available to the most of nuclear medicines services in Brazil and abroad. To overcome the problem, a new trend is presented in this work, implementing computational models to balance the breast attenuation effects on the left ventricle anterior wall, during myocardium perfusion scintigraphy procedures with SPECT. A neural network was put on in order to provide the attenuation correction indexes, based upon the following patients individual biotypes features: mass, age, height, chest and breast thicknesses, heart size, as well as the imparted activity intake levels. (author)

Practical method of breast attenuation correction for cardiac SPECT

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Anderson de; Nogueira, Tindyua; Gutterres, Ricardo Fraga [Comissao Nacional de Energia Nuclear (CNEN), Rio de Janeiro, RJ (Brazil). Coordenacao Geral de Instalacoes Medicas e Industriais (CGMI)]. E-mails: anderson@cnen.gov.br; tnogueira@cnen.gov.br; rguterre@cnen.gov.br; Megueriam, Berdj Aram [Instituto Nacional do Cancer (INCA), Rio de Janeiro, RJ (Brazil)]. E-mail: megueriam@hotmail.com; Santos, Goncalo Rodrigues dos [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil)]. E-mail: goncalo@cnen.gov.br

2007-07-01

The breast attenuation effects on SPECT (Single Photon Emission Tomography) myocardium perfusion procedures have been lately scope of continuous inquiry. The requested attenuation correction factors are usually achieved by transmission analysis, making up the exposure of a standard external source to the SPECT, as a routine step. However, its high cost makes this methodology not fully available to the most of nuclear medicines services in Brazil and abroad. To overcome the problem, a new trend is presented in this work, implementing computational models to balance the breast attenuation effects on the left ventricle anterior wall, during myocardium perfusion scintigraphy procedures with SPECT. A neural network was put on in order to provide the attenuation correction indexes, based upon the following patients individual biotypes features: mass, age, height, chest and breast thicknesses, heart size, as well as the imparted activity intake levels. (author)

Attenuation correction for the NIH ATLAS small animal PET scanner

CERN Document Server

Yao, Rutao; Liow, JeihSan; Seidel, Jurgen

2003-01-01

We evaluated two methods of attenuation correction for the NIH ATLAS small animal PET scanner: 1) a CT-based method that derives 511 keV attenuation coefficients (mu) by extrapolation from spatially registered CT images; and 2) an analytic method based on the body outline of emission images and an empirical mu. A specially fabricated attenuation calibration phantom with cylindrical inserts that mimic different body tissues was used to derive the relationship to convert CT values to (I for PET. The methods were applied to three test data sets: 1) a uniform cylinder phantom, 2) the attenuation calibration phantom, and 3) a mouse injected with left bracket **1**8F right bracket FDG. The CT-based attenuation correction factors were larger in non-uniform regions of the imaging subject, e.g. mouse head, than the analytic method. The two methods had similar correction factors for regions with uniform density and detectable emission source distributions.

Acousto-optic measurements of ultrasound attenuation in tellurium dioxide crystal

International Nuclear Information System (INIS)

Voloshinov, V. B.; Lemyaskina, E. A.

1996-01-01

The paper is devoted to experimental investigation of ultrasound propagation in tellurium dioxide monocrystal. In particular, attenuation of slow shear acoustic modes in the crystal was measured. The measurements were performed by acousto-optic methods using probing of acoustic column by a laser beam. The paper describes measurements of acoustic attenuation coefficient for slow shear ultrasonic waves propagating at an angle =4.5 O with respect to the (110) direction in the (110) plane. The investigation was made at acoustic frequency f = 100 MHz with pulsed acoustic waves and with an optical beam of a He-Ne laser. It is found that the attenuation coefficient is α = 0.57 cm -1 ± 15 %. The attenuation at acoustic frequencies f ≥ 100 MHz influences performance characteristics of acousto-optical devices based on tellurium dioxide. As proved, spectral resolution of a quasicollinear acoustooptic filter decreases by a factor of 2 compared to a case of the attenuation absence. (authors)

Constant-work-space algorithms for geometric problems

Directory of Open Access Journals (Sweden)

Tetsuo Asano

2011-07-01

Full Text Available Constant-work-space algorithms may use only constantly many cells of storage in addition to their input, which is provided as a read-only array. We show how to construct several geometric structures efficiently in the constant-work-space model. Traditional algorithms process the input into a suitable data structure (like a doubly-connected edge list that allows efficient traversal of the structure at hand. In the constant-work-space setting, however, we cannot afford to do this. Instead, we provide operations that compute the desired features on the fly by accessing the input with no extra space. The whole geometric structure can be obtained by using these operations to enumerate all the features. Of course, we must pay for the space savings by slower running times. While the standard data structure allows us to implement traversal operations in constant time, our schemes typically take linear time to read the input data in each step.We begin with two simple problems: triangulating a planar point set and finding the trapezoidal decomposition of a simple polygon. In both cases adjacent features can be enumerated in linear time per step, resulting in total quadratic running time to output the whole structure. Actually, we show that the former result carries over to the Delaunay triangulation, and hence the Voronoi diagram. This also means that we can compute the largest empty circle of a planar point set in quadratic time and constant work-space. As another application, we demonstrate how to enumerate the features of an Euclidean minimum spanning tree (EMST in quadratic time per step, so that the whole EMST can be found in cubic time using constant work-space.Finally, we describe how to compute a shortest geodesic path between two points in a simple polygon. Although the shortest path problem in general graphs is NL-complete (Jakoby and Tantau 2003, this constrained problem can be solved in quadratic time using only constant work-space.

Lattice Boltzmann simulations of attenuation-driven acoustic streaming

International Nuclear Information System (INIS)

Haydock, David; Yeomans, J M

2003-01-01

We show that lattice Boltzmann simulations can be used to model the attenuation-driven acoustic streaming produced by a travelling wave. Comparisons are made to analytical results and to the streaming pattern produced by an imposed body force approximating the Reynolds stresses. We predict the streaming patterns around a porous material in an attenuating acoustic field

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.

Adaptive attenuation of aliased ground roll using the shearlet transform

Science.gov (United States)

Hosseini, Seyed Abolfazl; Javaherian, Abdolrahim; Hassani, Hossien; Torabi, Siyavash; Sadri, Maryam

2015-01-01

Attenuation of ground roll is an essential step in seismic data processing. Spatial aliasing of the ground roll may cause the overlap of the ground roll with reflections in the f-k domain. The shearlet transform is a directional and multidimensional transform that separates the events with different dips and generates subimages in different scales and directions. In this study, the shearlet transform was used adaptively to attenuate aliased and non-aliased ground roll. After defining a filtering zone, an input shot record is divided into segments. Each segment overlaps adjacent segments. To apply the shearlet transform on each segment, the subimages containing aliased and non-aliased ground roll, the locations of these events on each subimage are selected adaptively. Based on these locations, mute is applied on the selected subimages. The filtered segments are merged together, using the Hanning function, after applying the inverse shearlet transform. This adaptive process of ground roll attenuation was tested on synthetic data, and field shot records from west of Iran. Analysis of the results using the f-k spectra revealed that the non-aliased and most of the aliased ground roll were attenuated using the proposed adaptive attenuation procedure. Also, we applied this method on shot records of a 2D land survey, and the data sets before and after ground roll attenuation were stacked and compared. The stacked section after ground roll attenuation contained less linear ground roll noise and more continuous reflections in comparison with the stacked section before the ground roll attenuation. The proposed method has some drawbacks such as more run time in comparison with traditional methods such as f-k filtering and reduced performance when the dip and frequency content of aliased ground roll are the same as those of the reflections.

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.

Characterizing X-ray Attenuation of Containerized Cargo

Energy Technology Data Exchange (ETDEWEB)

Birrer, N. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Divin, C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Glenn, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Martz, H. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wang, G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2016-08-02

X-ray inspection systems can be used to detect radiological and nuclear threats in imported cargo. In order to better understand performance of these systems, the attenuation characteristics of imported cargo need to be determined. This project focused on developing image processing algorithms for segmenting cargo and using x-ray attenuation to quantify equivalent steel thickness to determine cargo density. These algorithms were applied to over 450 cargo radiographs. The results are summarized in this report.

Globally Coupled Chaotic Maps with Constant Force

International Nuclear Information System (INIS)

Li Jinghui

2008-01-01

We investigate the motion of the globally coupled maps (logistic map) with a constant force. It is shown that the constant force can cause multi-synchronization for the globally coupled chaotic maps studied by us.

A novel phantom design for emission tomography enabling scatter- and attenuation-''free'' single-photon emission tomography imaging

International Nuclear Information System (INIS)

Larsson, S.A.; Johansson, L.; Jonsson, C.; Pagani, M.; Jacobsson, H.

2000-01-01

A newly designed technique for experimental single-photon emission tomography (SPET) and positron emission tomography (PET) data acquisition with minor disturbing effects from scatter and attenuation has been developed. In principle, the method is based on discrete sampling of the radioactivity distribution in 3D objects by means of equidistant 2D planes. The starting point is a set of digitised 2D sections representing the radioactivity distribution of the 3D object. Having a radioactivity-related grey scale, the 2D images are printed on paper sheets using radioactive ink. The radioactive sheets can be shaped to the outline of the object and stacked into a 3D structure with air or some arbitrary dense material in between. For this work, equidistantly spaced transverse images of a uniform cylindrical phantom and of the digitised Hoffman rCBF phantom were selected and printed out on paper sheets. The uniform radioactivity sheets were imaged on the surface of a low-energy ultra-high-resolution collimator (4 mm full-width at half-maximum) of a three-headed SPET camera. The reproducibility was 0.7% and the uniformity was 1.2%. Each rCBF sheet, containing between 8.3 and 80 MBq of 99m TcO 4 - depending on size, was first imaged on the collimator and then stacked into a 3D structure with constant 12 mm air spacing between the slices. SPET was performed with the sheets perpendicular to the central axis of the camera. The total weight of the stacked rCBF phantom in air was 63 g, giving a scatter contribution comparable to that of a point source in air. The overall attenuation losses were <20%. A second SPET study was performed with 12-mm polystyrene plates in between the radioactive sheets. With polystyrene plates, the total phantom weight was 2300 g, giving a scatter and attenuation magnitude similar to that of a patient study. With the proposed technique, it is possible to obtain ''ideal'' experimental images (essentially built up by primary photons) for comparison with

Equilibrium-constant expressions for aqueous plutonium

International Nuclear Information System (INIS)

Silver, G.L.

2010-01-01

Equilibrium-constant expressions for Pu disproportionation reactions traditionally contain three or four terms representing the concentrations or fractions of the oxidation states. The expressions can be rewritten so that one of the oxidation states is replaced by a term containing the oxidation number of the plutonium. Experimental estimations of the numerical values of the constants can then be checked in several ways. (author)

Multiple constant multiplication optimizations for field programmable gate arrays

CERN Document Server

Kumm, Martin

2016-01-01

This work covers field programmable gate array (FPGA)-specific optimizations of circuits computing the multiplication of a variable by several constants, commonly denoted as multiple constant multiplication (MCM). These optimizations focus on low resource usage but high performance. They comprise the use of fast carry-chains in adder-based constant multiplications including ternary (3-input) adders as well as the integration of look-up table-based constant multipliers and embedded multipliers to get the optimal mapping to modern FPGAs. The proposed methods can be used for the efficient implementation of digital filters, discrete transforms and many other circuits in the domain of digital signal processing, communication and image processing. Contents Heuristic and ILP-Based Optimal Solutions for the Pipelined Multiple Constant Multiplication Problem Methods to Integrate Embedded Multipliers, LUT-Based Constant Multipliers and Ternary (3-Input) Adders An Optimized Multiple Constant Multiplication Architecture ...

Using Auditory Steady-State Responses for Measuring Hearing Protector Attenuation

Directory of Open Access Journals (Sweden)

Olivier Valentin

2017-01-01

Full Text Available Introduction: Present methods of measuring the attenuation of hearing protection devices (HPDs have limitations. Objective measurements such as field microphone in real-ear do not assess bone-conducted sound. Psychophysical measurements such as real-ear attenuation at threshold (REAT are biased due to the low frequency masking effects from test subjects’ physiological noise and the variability of measurements based on subjective responses. An auditory steady-state responses (ASSRs procedure is explored as a technique which might overcome these limitations. Subjects and Methods: Pure tone stimuli (500 and 1000 Hz, amplitude modulated at 40 Hz, are presented to 10 normal-hearing adults through headphones at three levels in 10 dB steps. Two conditions were assessed: unoccluded ear canal and occluded ear canal. ASSR amplitude data as a function of the stimulation level are linearized using least-square regressions. The “physiological attenuation” is then calculated as the average difference between the two measurements. The technical feasibility of measuring earplug attenuation is demonstrated for the group average attenuation across subjects. Results: No significant statistical difference is found between the average REAT attenuation and the average ASSR-based attenuation. Conclusion: Feasibility is not yet demonstrated for individual subjects since differences between the estimates occurred for some subjects.

Analytical inversion formula for uniformly attenuated fan-beam projections

International Nuclear Information System (INIS)

Weng, Y.; Zeng, G.L.; Gullberg, G.T.

1997-01-01

In deriving algorithms to reconstruct single photon emission computed tomography (SPECT) projection data, it is important that the algorithm compensates for photon attenuation in order to obtain quantitative reconstruction results. A convolution backprojection algorithm was derived by Tretiak and Metz to reconstruct two-dimensional (2-D) transaxial slices from uniformly attenuated parallel-beam projections. Using transformation of coordinates, this algorithm can be modified to obtain a formulation useful to reconstruct uniformly attenuated fan-beam projections. Unlike that for parallel-beam projections, this formulation does not produce a filtered backprojection reconstruction algorithm but instead has a formulation that is an inverse integral operator with a spatially varying kernel. This algorithm thus requires more computation time than does the filtered backprojection reconstruction algorithm for the uniformly attenuated parallel-beam case. However, the fan-beam reconstructions demonstrate the same image quality as that of parallel-beam reconstructions

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

Dynamic Characteristics of The DSI-Type Constant-Flow Valves

Science.gov (United States)

Kang, Yuan; Hu, Sheng-Yan; Chou, Hsien-Chin; Lee, Hsing-Han

Constant flow valves have been presented in industrial applications or academic studies, which compensate recess pressures of a hydrostatic bearing to resist load fluctuating. The flow rate of constant-flow valves can be constant in spite of the pressure changes in recesses, however the design parameters must be specified. This paper analyzes the dynamic responses of DSI-type constant-flow valves that is designed as double pistons on both ends of a spool with single feedback of working pressure and regulating restriction at inlet. In this study the static analysis presents the specific relationships among design parameters for constant flow rate and the dynamic analyses give the variations around the constant flow rate as the working pressure fluctuates.

Brunenders: a partially attenuated historic poliovirus type I vaccine strain.

Science.gov (United States)

Sanders, Barbara P; Liu, Ying; Brandjes, Alies; van Hoek, Vladimir; de Los Rios Oakes, Isabel; Lewis, John; Wimmer, Eckard; Custers, Jerome H H V; Schuitemaker, Hanneke; Cello, Jeronimo; Edo-Matas, Diana

2015-09-01

Brunenders, a type I poliovirus (PV) strain, was developed in 1952 by J. F. Enders and colleagues through serial in vitro passaging of the parental Brunhilde strain, and was reported to display partial neuroattenuation in monkeys. This phenotype of attenuation encouraged two vaccine manufacturers to adopt Brunenders as the type I component for their inactivated poliovirus vaccines (IPVs) in the 1950s, although today no licensed IPV vaccine contains Brunenders. Here we confirmed, in a transgenic mouse model, the report of Enders on the reduced neurovirulence of Brunenders. Although dramatically neuroattenuated relative to WT PV strains, Brunenders remains more virulent than the attenuated oral vaccine strain, Sabin 1. Importantly, the neuroattenuation of Brunenders does not affect in vitro growth kinetics and in vitro antigenicity, which were similar to those of Mahoney, the conventional type I IPV vaccine strain. We showed, by full nucleotide sequencing, that Brunhilde and Brunenders differ at 31 nucleotides, eight of which lead to amino acid changes, all located in the capsid. Upon exchanging the Brunenders capsid sequence with that of the Mahoney capsid, WT neurovirulence was regained in vivo, suggesting a role for the capsid mutations in Brunenders attenuation. To date, as polio eradication draws closer, the switch to using attenuated strains for IPV is actively being pursued. Brunenders preceded this novel strategy as a partially attenuated IPV strain, accompanied by decades of successful use in the field. Providing data on the attenuation of Brunenders may be of value in the further construction of attenuated PV strains to support the grand pursuit of the global eradication of poliomyelitis.

FOREWORD: International determination of the Avogadro constant International determination of the Avogadro constant

Science.gov (United States)

Massa, Enrico; Nicolaus, Arnold

2011-04-01

This issue of Metrologia collects papers about the results of an international research project aimed at the determination of the Avogadro constant, NA, by counting the atoms in a silicon crystal highly enriched with the isotope 28Si. Fifty years ago, Egidi [1] thought about realizing an atomic mass standard. In 1965, Bonse and Hart [2] operated the first x-ray interferometer, thus paving the way to the achievement of Egidi's dream, and soon Deslattes et al [3] completed the first counting of the atoms in a natural silicon crystal. The present project, outlined by Zosi [4] in 1983, began in 2004 by combining the experiences and capabilities of the BIPM, INRIM, IRMM, NIST, NPL, NMIA, NMIJ and PTB. The start signal, ratified by a memorandum of understanding, was a contract for the production of a silicon crystal highly enriched with 28Si. The enrichment process was undertaken by the Central Design Bureau of Machine Building in St Petersburg. Subsequently, a polycrystal was grown in the Institute of Chemistry of High-Purity Substances of the Russian Academy of Sciences in Nizhny Novgorod and a 28Si boule was grown and purified by the Leibniz-Institut für Kristallzüchtung in Berlin. Isotope enrichment made it possible to apply isotope dilution mass spectroscopy, to determine the Avogadro constant with unprecedented accuracy, and to fulfil Egidi's dream. To convey Egidi's 'fantasy' into practice, two 28Si kilogram prototypes shaped as quasi-perfect spheres were manufactured by the Australian Centre for Precision Optics; their isotopic composition, molar mass, mass, volume, density and lattice parameter were accurately determined and their surfaces were chemically and physically characterized at the atomic scale. The paper by Andreas et al reviews the work carried out; it collates all the findings and illustrates how Avogadro's constant was obtained. Impurity concentration and gradients in the enriched crystal were measured by infrared spectroscopy and taken into

Viability of natural attenuation in a petroleum-contaminated shallow sandy aquifer

International Nuclear Information System (INIS)

Lee, Jin-Yong; Lee, Kang-Kun

2003-01-01

More than 20 years would be required to clean up the site by natural attenuation alone. - This study focused on evaluating and quantifying the potential of natural attenuation of groundwater at a petroleum-contaminated site in an industrial area of a satellite city of Seoul, Korea. Groundwater at the study site was contaminated with toluene, ethylbenzene and xylene (TEX). Eight rounds of groundwater sampling and subsequent chemical analyses were performed over a period of 3 years. The groundwater quality data suggest that TEX concentrations at this site have been decreasing with time and that the TEX plume is at a quasi-steady state. Trend analysis, changes in mass flux and plume area also confirmed that the TEX plume has reached a quasi-steady state. The proportion of the total attenuation attributable to biodegradation has decreased over the monitoring period while contribution of other attenuation processes, such as dilution or dispersion, has increased. Based on the calculated attenuation rates, it would take more than 20 years to clean up the site by natural attenuation alone

Some comments on the universal constant in DSR

Energy Technology Data Exchange (ETDEWEB)

Girelli, Florian [SISSA, Via Beirut 2-4, 34014 Trieste (Italy); INFN, Sezione di Trieste (Italy); Livine, Etera R [Laborat. de Physique, ENS Lyon, CNRS UMR 5672, 46 Allee d' Italie, 69364 Lyon Cedex 07 (France)

2007-05-15

Deformed Special Relativity is usually presented as a deformation of Special Relativity accommodating a new universal constant, the Planck mass, while respecting the relativity principle. In order to avoid some fundamental problems (e.g. soccer ball problem), we argue that we should switch point of view and consider instead the Newton constant G as the universal constant.

Some comments on the universal constant in DSR

International Nuclear Information System (INIS)

Girelli, Florian; Livine, Etera R

2007-01-01

Deformed Special Relativity is usually presented as a deformation of Special Relativity accommodating a new universal constant, the Planck mass, while respecting the relativity principle. In order to avoid some fundamental problems (e.g. soccer ball problem), we argue that we should switch point of view and consider instead the Newton constant G as the universal constant

Radiation-induced attenuation in integrated optical materials

International Nuclear Information System (INIS)

Evans, B.D.

1989-01-01

This paper reports that three materials commonly employed in opto-electronic integrated circuits evaluated for radiation-induced optical attenuation in the range 300 nm to 3000 nm. These include optically clear epoxy and crystalline lithium niobate after Co-60 exposure and crystalline tellurium dioxide after mixed gamma/fast-neutron exposure. In all these materials, however, induced loss was restricted to shorter wavelengths; attenuation induced at the telecommunications windows near 850, 1300 and 1550 nm was <0.1 dB/cm

Principles underlying rational design of live attenuated influenza vaccines

Science.gov (United States)

Jang, Yo Han

2012-01-01

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

Cooperative effect of the attenuation determinants derived from poliovirus sabin 1 strain is essential for attenuation of enterovirus 71 in the NOD/SCID mouse infection model.

Science.gov (United States)

Arita, Minetaro; Ami, Yasushi; Wakita, Takaji; Shimizu, Hiroyuki

2008-02-01

Enterovirus 71 (EV71) is a causative agent of hand, foot, and mouth disease and is also associated with serious neurological disorders. An attenuated EV71 strain [EV71(S1-3')] has been established in the cynomolgus monkey infection model; this strain contains the attenuation determinants derived from the type 1 poliovirus vaccine strain, Sabin 1 [PV1(Sabin)], in the 5' nontranslated region (NTR), 3D polymerase, and 3' NTR. In this study, we analyzed the effect of the attenuation determinants of PV1(Sabin) on EV71 infection in a NOD/SCID mouse infection model. We isolated a mouse-adapted EV71 strain [EV71(NOD/SCID)] that causes paralysis of the hind limbs in 3- to 4-week-old NOD/SCID mice by adaptation of the virulent EV71(Nagoya) strain in the brains of NOD/SCID mice. A single mutation at nucleotide 2876 that caused an amino acid change in capsid protein VP1 (change of the glycine at position 145 to glutamic acid) was essential for the mouse-adapted phenotype in NOD/SCID mice. Next, we introduced attenuation determinants derived from PV1(Sabin) along with the mouse adaptation mutation into the EV71(Nagoya) genome. In 4-week-old mice, the determinants in the 3D polymerase and 3' NTR, which are the major temperature-sensitive determinants, had a strong effect on attenuation. In contrast, the effect of individual determinants was weak in 3-week-old NOD/SCID mice, and all the determinants were required for substantial attenuation. These results suggest that a cooperative effect of the attenuation determinants of PV1(Sabin) is essential for attenuated neurovirulence of EV71.

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.)

Cosmological constant is a conserved charge

Science.gov (United States)

Chernyavsky, Dmitry; Hajian, Kamal

2018-06-01

Cosmological constant can always be considered as the on-shell value of a top form in gravitational theories. The top form is the field strength of a gauge field, and the theory enjoys a gauge symmetry. We show that cosmological constant is the charge of the global part of the gauge symmetry, and is conserved irrespective of the dynamics of the metric and other fields. In addition, we introduce its conjugate chemical potential, and prove the generalized first law of thermodynamics which includes variation of cosmological constant as a conserved charge. We discuss how our new term in the first law is related to the volume–pressure term. In parallel with the seminal Wald entropy, this analysis suggests that pressure can also be considered as a conserved charge.

The cosmological constant problem

International Nuclear Information System (INIS)

Dolgov, A.D.

1989-05-01

A review of the cosmological term problem is presented. Baby universe model and the compensating field model are discussed. The importance of more accurate data on the Hubble constant and the Universe age is stressed. 18 refs

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)

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.

Minimal residual cone-beam reconstruction with attenuation correction in SPECT

International Nuclear Information System (INIS)

La, Valerie; Grangeat, Pierre

1998-01-01

This paper presents an iterative method based on the minimal residual algorithm for tomographic attenuation compensated reconstruction from attenuated cone-beam projections given the attenuation distribution. Unlike conjugate-gradient based reconstruction techniques, the proposed minimal residual based algorithm solves directly a quasisymmetric linear system, which is a preconditioned system. Thus it avoids the use of normal equations, which improves the convergence rate. Two main contributions are introduced. First, a regularization method is derived for quasisymmetric problems, based on a Tikhonov-Phillips regularization applied to the factorization of the symmetric part of the system matrix. This regularization is made spatially adaptive to avoid smoothing the region of interest. Second, our existing reconstruction algorithm for attenuation correction in parallel-beam geometry is extended to cone-beam geometry. A circular orbit is considered. Two preconditioning operators are proposed: the first one is Grangeat's inversion formula and the second one is Feldkamp's inversion formula. Experimental results obtained on simulated data are presented and the shadow zone effect on attenuated data is illustrated. (author)

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)

Bulk sample self-attenuation correction by transmission measurement

International Nuclear Information System (INIS)

Parker, J.L.; Reilly, T.D.

1976-01-01

Various methods used in either finding or avoiding the attenuation correction in the passive γ-ray assay of bulk samples are reviewed. Detailed consideration is given to the transmission method, which involves experimental determination of the sample linear attenuation coefficient by measuring the transmission through the sample of a beam of gamma rays from an external source. The method was applied to box- and cylindrically-shaped samples

Building evolutionary architectures support constant change

CERN Document Server

Ford, Neal; Kua, Patrick

2017-01-01

The software development ecosystem is constantly changing, providing a constant stream of new tools, frameworks, techniques, and paradigms. Over the past few years, incremental developments in core engineering practices for software development have created the foundations for rethinking how architecture changes over time, along with ways to protect important architectural characteristics as it evolves. This practical guide ties those parts together with a new way to think about architecture and time.

An acoustic eikonal equation for attenuating transversely isotropic media with a vertical symmetry axis

KAUST Repository

Hao, Qi

2016-11-21

Seismic-wave attenuation is an important component of describing wave propagation. Certain regions, such as gas clouds inside the earth, exert highly localized attenuation. In fact, the anisotropic nature of the earth induces anisotropic attenuation because the quasi P-wave dispersion effect should be profound along the symmetry direction. We have developed a 2D acoustic eikonal equation governing the complex-valued traveltime of quasi P-waves in attenuating, transversely isotropic media with a vertical-symmetry axis (VTI). This equation is derived under the assumption that the complex-valued traveltime of quasi P-waves in attenuating VTI media are independent of the S-wave velocity parameter υS0 in Thomsen\\'s notation and the S-wave attenuation coefficient AS0 in Zhu and Tsvankin\\'s notation. We combine perturbation theory and Shanks transform to develop practical approximations to the acoustic attenuating eikonal equation, capable of admitting an analytical description of the attenuation in homogeneous media. For a horizontal-attenuating VTI layer, we also derive the nonhyperbolic approximations for the real and imaginary parts of the complex-valued reflection traveltime. These equations reveal that (1) the quasi SV-wave velocity and the corresponding quasi SV-wave attenuation coefficient given as part of Thomsen-type notation barely affect the ray velocity and ray attenuation of quasi P-waves in attenuating VTI media; (2) combining the perturbation method and Shanks transform provides an accurate analytic eikonal solution for homogeneous attenuating VTI media; (3) for a horizontal attenuating VTI layer with weak attenuation, the real part of the complex-valued reflection traveltime may still be described by the existing nonhyperbolic approximations developed for nonattenuating VTI media, and the imaginary part of the complex-valued reflection traveltime still has the shape of nonhyperbolic curves. In addition, we have evaluated the possible extension of the

ADVANCING THE SCIENCE OF NATURAL AND ENHANCED ATTENUATION FOR CHLORINATED SOLVENTS

Energy Technology Data Exchange (ETDEWEB)

Looney, B; TOM O. EARLY, T; TYLER GILMORE, T; FRANCIS H. CHAPELLE, F; NORMAN H. CUTSHALL, N; JEFF ROSS, J; MARK ANKENY, M; Michael Heitkamp, M; DAVID MAJOR, D; CHARLES J. NEWELL, C; W. JODY WAUGH, W; GARY WEIN, G; Karen Vangelas, K; Karen-M Adams, K; CLAIRE H. SINK, C

2006-12-27

This report summarizes the results of a three-year program that addressed key scientific and technical aspects related to natural and enhanced attenuation of chlorinated organics. The results from this coordinated three-year program support a variety of technical and regulatory advancements. Scientists, regulators, engineers, end-users and stakeholders participated in the program, which was supported by the U.S. Department of Energy (DOE) and the Interstate Technology and Regulatory Council (ITRC). The overarching objective of the effort was to examine environmental remedies that are based on natural processes--remedies such as Monitored Natural Attenuation (MNA) or Enhanced Attenuation (EA). A key result of the recent effort was the general affirmation of the approaches and guidance in the original U.S. Environmental Protection Agency (EPA) chlorinated solvent MNA protocols and directives from 1998 and 1999, respectively. The research program did identify several specific opportunities for advances based on: (1) mass balance as the central framework for attenuation based remedies, (2) scientific advancements and achievements during the past ten years, (3) regulatory and policy development and real-world experience using MNA, and (4) exploration of various ideas for integrating attenuation remedies into a systematic set of ''combined remedies'' for contaminated sites. These opportunities are summarized herein and are addressed in more detail in referenced project documents and journal articles, as well as in the technical and regulatory documents being developed within the ITRC. Natural attenuation processes occur in all soil and groundwater systems and act, to varying degrees, on all contaminants. Thus, a decision to rely on natural attenuation processes as part of a site-remediation strategy does not depend on the occurrence of natural attenuation, but on its effectiveness in meeting site-specific remediation goals. Meeting these goals

Developement of a Light Attenuator Based on Glassy Reflections ...

African Journals Online (AJOL)

The light intensity control of a luminous source is a very important operation in many optical applications. Several types of light attenuator exploiting different optical phenomena like diffraction, absorption, and reflection exist and they differ principally in the maximum attenuation rate, the control range, the sensitivity and the ...

Experiment evaluation of impact attenuator for a racing car under static load

Science.gov (United States)

Imanullah, Fahmi; Ubaidillah, Prasojo, Arfi Singgih; Wirawan, Adhe Aji

2018-02-01

The automotive world is a world where one of the factors that must be considered carefully is the safety aspect. In the formula student car one of the safety factor in the form of impact attenuator. Impact attenuator is used as anchoring when a collision occurs in front of the vehicle. In the rule of formula society of automotive engineer (FSAE) student, impact attenuator is required to absorb the energy must meet or exceed 7350 Joules with a slowdown in speed not exceeding 20 g average and peak of 40 g. The student formula participants are challenged to pass the boundaries so that in designing and making the impact attenuator must pay attention to the strength and use of the minimum material so that it can minimize the expenditure. In this work, an impact attenuator was fabricated and tested using static compression. The primary goal was evaluating the actual capability of the impact attenuator for impact energy absorption. The prototype was made of aluminum alloy in a prismatic shape, and the inside wall was filled with rooftop plastic slices and polyurethane hard foam. The compression test has successfully carried out, and the load versus displacement data could be used in calculating energy absorption capability. The result of the absorbent energy of the selected impact attenuator material. Impact attenuator full polyurethane absorbed energy reach 6380 Joule. For impact attenuator with aluminum polyurethane with a slashed rooftop material as section absorbed energy reach 6600 Joule. Impact attenuator with Aluminum Polyurethane with aluminum orange peel partitions absorbed energy reach 8800 Joule. From standard student formula, energy absorbed in this event must meet or exceed 7350 Joules that meet aluminum polyurethane with aluminum orange peel partitions with the ability to absorb 8800 Joule.

A null test of the cosmological constant

International Nuclear Information System (INIS)

Chiba, Takeshi; Nakamura, Takashi

2007-01-01

We provide a consistency relation between cosmological observables in general relativity with the cosmological constant. Breaking of this relation at any redshift would imply the breakdown of the hypothesis of the cosmological constant as an explanation of the current acceleration of the universe. (author)

On the constants for some Sobolev imbeddings

Directory of Open Access Journals (Sweden)

Pizzocchero Livio

2001-01-01

Full Text Available We consider the imbedding inequality is the Sobolev space (or Bessel potential space of type and (integer or fractional order . We write down upper bounds for the constants , using an argument previously applied in the literature in particular cases. We prove that the upper bounds computed in this way are in fact the sharp constants if , , and exhibit the maximising functions. Furthermore, using convenient trial functions, we derive lower bounds on for in many cases these are close to the previous upper bounds, as illustrated by a number of examples, thus characterizing the sharp constants with little uncertainty.

Cosmological constant and advanced gravitational wave detectors

International Nuclear Information System (INIS)

Wang, Y.; Turner, E.L.

1997-01-01

Interferometric gravitational wave detectors could measure the frequency sweep of a binary inspiral (characterized by its chirp mass) to high accuracy. The observed chirp mass is the intrinsic chirp mass of the binary source multiplied by (1+z), where z is the redshift of the source. Assuming a nonzero cosmological constant, we compute the expected redshift distribution of observed events for an advanced LIGO detector. We find that the redshift distribution has a robust and sizable dependence on the cosmological constant; the data from advanced LIGO detectors could provide an independent measurement of the cosmological constant. copyright 1997 The American Physical Society

Stability constants for silicate adsorbed to ferrihydrite

DEFF Research Database (Denmark)

Hansen, Hans Christian Bruun; Wetche, T.P.; Raulund-Rasmussen, Karsten

1994-01-01

Intrinsic surface acidity constants (K(a1)intr, K(a2)intr) and surface complexation constant for adsorption of orthosilicate onto synthetic ferrihydrite (K(Si) for the complex = FeOSi(OH)3) have been determined from acid/base titrations in 0.001-0.1 m NaClO4 electrolytes and silicate adsorption...... experiments in 0.01 m NaNO3 electrolyte (pH 3-6). The surface equilibrium constants were calculated according to the two-layer model by Dzombak & Morel (1990). Near equilibrium between protons/hydroxyls in solution and the ferrihydrite surface was obtained within minutes while equilibration with silicate...

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.

Validity of the CT to attenuation coefficient map conversion methods

International Nuclear Information System (INIS)

Faghihi, R.; Ahangari Shahdehi, R.; Fazilat Moadeli, M.

2004-01-01

The most important commercialized methods of attenuation correction in SPECT are based on attenuation coefficient map from a transmission imaging method. The transmission imaging system can be the linear source of radioelement or a X-ray CT system. The image of transmission imaging system is not useful unless to replacement of the attenuation coefficient or CT number with the attenuation coefficient in SPECT energy. In this paper we essay to evaluate the validity and estimate the error of the most used method of this transformation. The final result shows that the methods which use a linear or multi-linear curve accept a error in their estimation. The value of mA is not important but the patient thickness is very important and it can introduce a error more than 10 percent in the final result

Live attenuated S. Typhimurium vaccine with improved safety in immuno-compromised mice.

Directory of Open Access Journals (Sweden)

Balamurugan Periaswamy

Full Text Available Live attenuated vaccines are of great value for preventing infectious diseases. They represent a delicate compromise between sufficient colonization-mediated adaptive immunity and minimizing the risk for infection by the vaccine strain itself. Immune defects can predispose to vaccine strain infections. It has remained unclear whether vaccine safety could be improved via mutations attenuating a vaccine in immune-deficient individuals without compromising the vaccine's performance in the normal host. We have addressed this hypothesis using a mouse model for Salmonella diarrhea and a live attenuated Salmonella Typhimurium strain (ssaV. Vaccination with this strain elicited protective immunity in wild type mice, but a fatal systemic infection in immune-deficient cybb(-/-nos2(-/- animals lacking NADPH oxidase and inducible NO synthase. In cybb(-/-nos2(-/- mice, we analyzed the attenuation of 35 ssaV strains carrying one additional mutation each. One strain, Z234 (ssaV SL1344_3093, was >1000-fold attenuated in cybb(-/-nos2(-/- mice and ≈100 fold attenuated in tnfr1(-/- animals. However, in wt mice, Z234 was as efficient as ssaV with respect to host colonization and the elicitation of a protective, O-antigen specific mucosal secretory IgA (sIgA response. These data suggest that it is possible to engineer live attenuated vaccines which are specifically attenuated in immuno-compromised hosts. This might help to improve vaccine safety.

Macroseismic intensity attenuation in Iran

Science.gov (United States)

Yaghmaei-Sabegh, Saman

2018-01-01

Macroseismic intensity data plays an important role in the process of seismic hazard analysis as well in developing of reliable earthquake loss models. This paper presents a physical-based model to predict macroseismic intensity attenuation based on 560 intensity data obtained in Iran in the time period 1975-2013. The geometric spreading and energy absorption of seismic waves have been considered in the proposed model. The proposed easy to implement relation describes the intensity simply as a function of moment magnitude, source to site distance and focal depth. The prediction capability of the proposed model is assessed by means of residuals analysis. Prediction results have been compared with those of other intensity prediction models for Italy, Turkey, Iran and central Asia. The results indicate the higher attenuation rate for the study area in distances less than 70km.

DETERMINATION OF STABILITY CONSTANTS OF MANGANESE (II ...

African Journals Online (AJOL)

DR. AMINU

Keywords: Amino acids, dissociation constant, potentiometry, stability constant. INTRODUCTION. Acids – base titration involves the gradual addition or removal of protons for example using the deprotic form of glycine. The plot has two distinct stages corresponding to the deprotonation of the two different groups on glycine.

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

Constant voltage and constant current control implementation for electric vehicles (evs) wireless charger

Science.gov (United States)

Tampubolon, Marojahan; Pamungkas, Laskar; Hsieh, Yao Ching; Chiu, Huang Jen

2018-04-01

This paper presents the implementation of Constant Voltage (CV) and Constant Current (CC) control for a wireless charger system. A battery charging system needs these control modes to ensure the safety of the battery and the effectiveness of the charging system. Here, the wireless charger system does not employ any post-regulator stage to control the output voltage and output current of the charger. But, it uses a variable frequency control incorporated with a conventional PI control. As a result, the size and the weight of the system are reduced. This paper discusses the brief review of the SS-WPT, control strategy and implementation of the CV and CC control. Experimental hardware with 2kW output power has been performed and tested. The results show that the proposed CV and CC control method works well with the system.

Hydrolysis and formation constants at 250C

International Nuclear Information System (INIS)

Phillips, S.L.

1982-05-01

A database consisting of hydrolysis and formation constants for about 20 metals associated with the disposal of nuclear waste is given. Complexing ligands for the various ionic species of these metals include OH, F, Cl, SO 4 , PO 4 and CO 3 . Table 1 consists of tabulated calculated and experimental values of log K/sub xy/, mainly at 25 0 C and various ionic strengths together with references to the origin of the data. Table 2 consists of a column of recommended stability constants at 25 0 C and zero ionic strength tabulated in the column headed log K/sub xy/(0); other columns contain coefficients for an extended Debye-Huckel equation to permit calculations of stability constants up to 3 ionic strength, and up to 0.7 ionic strength using the Davies equation. Selected stability constants calculated with these coefficients for various ionic strengths agree to an average of +- 2% when compared with published experimental and calculated values

Whole-body PET/MRI: The effect of bone attenuation during MR-based attenuation correction in oncology imaging

Energy Technology Data Exchange (ETDEWEB)

Aznar, M.C., E-mail: marianne.aznar@regionh.dk [Department of Oncology, Section of Radiotherapy 3994, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen (Denmark); Sersar, R., E-mail: rachidadk@hotmail.com [DTU Informatics, Technical University of Denmark, Kongens Lyngby (Denmark); Saabye, J., E-mail: julie_saa@hotmail.com [DTU Informatics, Technical University of Denmark, Kongens Lyngby (Denmark); Ladefoged, C.N., E-mail: claesnl@gmail.com [Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Copenhagen (Denmark); Andersen, F.L., E-mail: Flemming.Andersen@regionh.dk [Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Copenhagen (Denmark); Rasmussen, J.H., E-mail: jacobrasmu@gmail.com [Department of Oncology, Section of Radiotherapy 3994, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen (Denmark); Löfgren, J., E-mail: Johan.Loefgren@regionh.dk [Department of Clinical Physiology, Nuclear Medicine and PET, Rigshospitalet, Copenhagen (Denmark); Beyer, T., E-mail: thomas.beyer@meduniwien.ac.at [Centre for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna (Austria)

2014-07-15

Purpose: In combined PET/MRI standard PET attenuation correction (AC) is based on tissue segmentation following dedicated MR sequencing and, typically, bone tissue is not represented. We evaluate PET quantification in whole-body (WB)-PET/MRI following MR-AC without considering bone attenuation and then investigate different strategies to account for bone tissue in clinical PET/MR imaging. To this purpose, bone tissue representation was extracted from separate CT images, and different bone representations were simulated from hypothetically derived MR-based bone classifications. Methods: Twenty oncology patients referred for a PET/CT were injected with either [18F]-FDG or [18F]-NaF and imaged on PET/CT (Biograph TruePoint/mCT, Siemens) and PET/MRI (mMR, Siemens) following a standard single-injection, dual-imaging clinical WB-protocol. Routine MR-AC was based on in-/opposed-phase MR imaging (orgMR-AC). PET(/MRI) images were reconstructed (AW-OSEM, 3 iterations, 21 subsets, 4 mm Gaussian) following routine MR-AC and MR-AC based on four modified attenuation maps. These modified attenuation maps were created for each patient by non-linear co-registration of the CT images to the orgMR-AC images, and adding CT bone mask values representing cortical bone: 1200 HU (cortCT), spongiosa bone: 350 HU (spongCT), average CT value (meanCT) and original CT values (orgCT). Relative difference images of the PET following AC using the modified attenuation maps were compared. SUVmean was calculated in anatomical reference regions and for PET-positive lesions. Results: The relative differences in SUVmean across patients following orgMR-AC and orgCT in soft tissue lesions and in bone lesions were similar (range: 0.0% to −22.5%), with an average underestimation of SUVmean of 7.2% and 10.0%, respectively when using orgMR-AC. In bone lesions, spongCT values were closest to orgCT (median bias of 1.3%, range: –9.0% to 13.5%) while the overestimation of SUVmean with respect to orgCT was

f(R) constant-roll inflation

Energy Technology Data Exchange (ETDEWEB)

Motohashi, Hayato [Universidad de Valencia-CSIC, Instituto de Fisica Corpuscular (IFIC), Valencia (Spain); Starobinsky, Alexei A. [L.D. Landau Institute for Theoretical Physics, RAS, Moscow (Russian Federation); National Research University Higher School of Economics, Moscow (Russian Federation)

2017-08-15

The previously introduced class of two-parametric phenomenological inflationary models in general relativity in which the slow-roll assumption is replaced by the more general, constant-roll condition is generalized to the case of f(R) gravity. A simple constant-roll condition is defined in the original Jordan frame, and exact expressions for a scalaron potential in the Einstein frame, for a function f(R) (in the parametric form) and for inflationary dynamics are obtained. The region of the model parameters permitted by the latest observational constraints on the scalar spectral index and the tensor-to-scalar ratio of primordial metric perturbations generated during inflation is determined. (orig.)

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.

Vibrational modes of hydraulic fractures: Inference of fracture geometry from resonant frequencies and attenuation

Science.gov (United States)

Lipovsky, Bradley P.; Dunham, Eric M.

2015-02-01

Oscillatory seismic signals arising from resonant vibrations of hydraulic fractures are observed in many geologic systems, including volcanoes, glaciers and ice sheets, and hydrocarbon and geothermal reservoirs. To better quantify the physical dimensions of fluid-filled cracks and properties of the fluids within them, we study wave motion along a thin hydraulic fracture waveguide. We present a linearized analysis, valid at wavelengths greater than the fracture aperture, that accounts for quasi-static elastic deformation of the fracture walls, as well as fluid viscosity, inertia, and compressibility. In the long-wavelength limit, anomalously dispersed guided waves known as crack or Krauklis waves propagate with restoring force from fracture wall elasticity. At shorter wavelengths, the waves become sound waves within the fluid channel. Wave attenuation in our model is due to fluid viscosity, rather than seismic radiation from crack tips or fracture wall roughness. We characterize viscous damping at both low frequencies, where the flow is always fully developed, and at high frequencies, where the flow has a nearly constant velocity profile away from viscous boundary layers near the fracture walls. Most observable seismic signals from resonating fractures likely arise in the boundary layer crack wave limit, where fluid-solid coupling is pronounced and attenuation is minimal. We present a method to estimate the aperture and length of a resonating hydraulic fracture using both the seismically observed quality factor and characteristic frequency. Finally, we develop scaling relations between seismic moment and characteristic frequency that might be useful when interpreting the statistics of hydraulic fracture events.

Statistical problems with weather-radar images, II: Attenuation detection

International Nuclear Information System (INIS)

Fernandez-Duran, Juan-Jose; Upton, Graham

2003-01-01

A procedure based on the combination of a Bayesian changepoint model and ordinary least squares is used to identify and quantify regions where a radar signal has been attenuated (i.e.diminished) as a consequence of intervening weather. A graphical polar display is introduced that illustrates the location and importance of the attenuation

Dynamics of the cosmological and Newton’s constant

International Nuclear Information System (INIS)

Smolin, Lee

2016-01-01

A modification of general relativity is presented in which Newton’s constant, G, and the cosmological constant, Λ, become a conjugate pair of dynamical variables. These are functions of a global time, hence the theory is presented in the framework of shape dynamics, which trades many-fingered time for a local scale invariance and an overall reparametrization of the global time. As a result, due to the fact that these global dynamical variables are canonically conjugate, the field equations are consistent. The theory predicts a relationship with no free parameters between the rates of change of Newton’s constant and the cosmological constant, in terms of the spatial average of the matter Lagrangian density. (paper)

Higher success rate with transcranial electrical stimulation of motor-evoked potentials using constant-voltage stimulation compared with constant-current stimulation in patients undergoing spinal surgery.

Science.gov (United States)

Shigematsu, Hideki; Kawaguchi, Masahiko; Hayashi, Hironobu; Takatani, Tsunenori; Iwata, Eiichiro; Tanaka, Masato; Okuda, Akinori; Morimoto, Yasuhiko; Masuda, Keisuke; Tanaka, Yuu; Tanaka, Yasuhito

2017-10-01

During spine surgery, the spinal cord is electrophysiologically monitored via transcranial electrical stimulation of motor-evoked potentials (TES-MEPs) to prevent injury. Transcranial electrical stimulation of motor-evoked potential involves the use of either constant-current or constant-voltage stimulation; however, there are few comparative data available regarding their ability to adequately elicit compound motor action potentials. We hypothesized that the success rates of TES-MEP recordings would be similar between constant-current and constant-voltage stimulations in patients undergoing spine surgery. The objective of this study was to compare the success rates of TES-MEP recordings between constant-current and constant-voltage stimulation. This is a prospective, within-subject study. Data from 100 patients undergoing spinal surgery at the cervical, thoracic, or lumbar level were analyzed. The success rates of the TES-MEP recordings from each muscle were examined. Transcranial electrical stimulation with constant-current and constant-voltage stimulations at the C3 and C4 electrode positions (international "10-20" system) was applied to each patient. Compound muscle action potentials were bilaterally recorded from the abductor pollicis brevis (APB), deltoid (Del), abductor hallucis (AH), tibialis anterior (TA), gastrocnemius (GC), and quadriceps (Quad) muscles. The success rates of the TES-MEP recordings from the right Del, right APB, bilateral Quad, right TA, right GC, and bilateral AH muscles were significantly higher using constant-voltage stimulation than those using constant-current stimulation. The overall success rates with constant-voltage and constant-current stimulations were 86.3% and 68.8%, respectively (risk ratio 1.25 [95% confidence interval: 1.20-1.31]). The success rates of TES-MEP recordings were higher using constant-voltage stimulation compared with constant-current stimulation in patients undergoing spinal surgery. Copyright © 2017

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

Using Tectonic Tremor to Constrain Seismic-wave Attenuation in Cascadia

Science.gov (United States)

Littel, G.; Thomas, A.; Baltay, A.

2017-12-01

In addition to fast, seismic slip, many subduction zones also host slow, largely aseismic slip, accompanied by a weak seismic signal known as tectonic tremor. Tremor is a small amplitude, low-frequency seismic signal that originates at the plate interface, down-dip of where large earthquakes typically occur. The Cascadia subduction zone has not seen a large megathrust earthquake since 1700, yet its recurrence interval of 350-500 years motivates heightened interest in understanding the seismic hazard of the region. Of great importance is to understand the degree to which waves are attenuated as they leave the plate interface and travel towards populated regions of interest. Ground motion prediction equations (GMPEs) relate ground motion to a number of parameters, including earthquake magnitude, depth, style of faulting, and anelastic attenuation, and are typically determined empirically from earthquake ground motion recordings. In Cascadia, however, earthquakes of the moderate size typically used to constrain GMPEs occur relatively infrequently compared to tectonic tremor events, which, in contrast, occur periodically approximately every 10-19 months. Studies have shown that the abundant tectonic tremor in Cascadia, despite its small amplitudes, can be used to constrain seismic wave attenuation in GMPEs. Here we quantify seismic wave attenuation and determine its spatial variations in Cascadia by performing an inversion using tremor ground motion amplitudes, taken as peak ground acceleration (PGA) and peak ground velocity (PGV) from 1 min window waveforms of each individual tremor event. We estimate the anelastic attenuation parameter for varying regional sections along the Cascadia margin. Changes in seismic-wave attenuation along the Cascadia Subduction Zone could result in significantly different ground motions in the event of a very large earthquake, hence quantifying attenuation may help to better estimate the severity of shaking in densely populated

Association constants of telluronium salts; Konstanty assotsiatsii telluronievykh solej

Energy Technology Data Exchange (ETDEWEB)

Kovach, N A; Rivkin, B B; Sadekov, T D; Shvajka, O P

1997-12-31

Association constants in acetonitrile of triphenyl telluronium salts, which are dilute electrolytes, are determined through the conductometry method. Satisfactory correlation dependence of constants of interion association and threshold molar electroconductivity on the Litvinenko-Popov constants for depositing groups is identified. 6 refs.

Identification of force constants in β-brass

DEFF Research Database (Denmark)

Norvell, J. C.; Als-Nielsen, Jens Aage

1969-01-01

The phonon dispersion curves of β-brass have previously been measured by Gilat and Dolling and a fit was obtained to a Born-von Kármán model with forces extending to the fourth nearest neighbours. Although a factor of 10 was found between the second-nearest-neighbour Cu-Cu and Zn-Zn force constants......, the data did not allow an identification of these constants. By comparisons of neutron group intensities from two β-brass crystals, one with normal Cu and the other isotopically enriched with 65Cu, we are able to identify conclusively these force constants: αZn-Zn2nd similar, equals 10αCu-Cu2nd....

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.

Analysis of the chemical equilibrium of combustion at constant volume

Directory of Open Access Journals (Sweden)

Marius BREBENEL

2014-04-01

Full Text Available Determining the composition of a mixture of combustion gases at a given temperature is based on chemical equilibrium, when the equilibrium constants are calculated on the assumption of constant pressure and temperature. In this paper, an analysis of changes occurring when combustion takes place at constant volume is presented, deriving a specific formula of the equilibrium constant. The simple reaction of carbon combustion in pure oxygen in both cases (constant pressure and constant volume is next considered as example of application, observing the changes occurring in the composition of the combustion gases depending on temperature.

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.

Viability of natural attenuation in a petroleum-contaminated shallow sandy aquifer

International Nuclear Information System (INIS)

Jin Yong Lee; Kang Kun Lee

2003-01-01

This study focused on evaluating and quantifying the potential of natural attenuation of groundwater at a petroleum-contaminated site in an industrial area of a satellite city of Seoul, Korea. Groundwater at the study site was contaminated with toluene, ethylbenzene and xylene (TEX). Eight rounds of groundwater sampling and subsequent chemical analyses were performed over a period of 3 years. The groundwater quality data suggest that TEX concentrations at this site have been decreasing with time and that the TEX plume is at a quasi-steady state. Trend analysis, changes in mass flux and plume area also confirmed that the TEX plume has reached a quasi-steady state. The proportion of the total attenuation attributable to biodegradation has decreased over the monitoring period while contribution of other attenuation processes, such as dilution or dispersion, has increased. Based on the calculated attenuation rates, it would take more than 20 years to clean up the site by natural attenuation alone. (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)

Constant Width Planar Computation Characterizes ACC0

DEFF Research Database (Denmark)

Hansen, Kristoffer Arnsfelt

2006-01-01

We obtain a characterization of ACC0 in terms of a natural class of constant width circuits, namely in terms of constant width polynomial size planar circuits. This is shown via a characterization of the class of acyclic digraphs which can be embedded on a cylinder surface in such a way that all...

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.

Stability constant of the trisglycinto metal complexes | Na'aliya ...

African Journals Online (AJOL)

The stability constants of iron, manganese, cobalt, and nickel complexes of glycine have been determined in aqueous solution by potentiometric titration with standard sodium hydroxide solution. The values of the stepwise stability constants were obtained by ORIGIN '50' program. The overall stability constants of the ...

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.

Seismic Full Waveform Modeling & Imaging in Attenuating Media

Science.gov (United States)

Guo, Peng

Seismic attenuation strongly affects seismic waveforms by amplitude loss and velocity dispersion. Without proper inclusion of Q parameters, errors can be introduced for seismic full waveform modeling and imaging. Three different (Carcione's, Robertsson's, and the generalized Robertsson's) isotropic viscoelastic wave equations based on the generalized standard linear solid (GSLS) are evaluated. The second-order displacement equations are derived, and used to demonstrate that, with the same stress relaxation times, these viscoelastic formulations are equivalent. By introducing separate memory variables for P and S relaxation functions, Robertsson's formulation is generalized to allow different P and S wave stress relaxation times, which improves the physical consistency of the Qp and Qs modelled in the seismograms.The three formulations have comparable computational cost. 3D seismic finite-difference forward modeling is applied to anisotropic viscoelastic media. The viscoelastic T-matrix (a dynamic effective medium theory) relates frequency-dependent anisotropic attenuation and velocity to reservoir properties in fractured HTI media, based on the meso-scale fluid flow attenuation mechanism. The seismic signatures resulting from changing viscoelastic reservoir properties are easily visible. Analysis of 3D viscoelastic seismograms suggests that anisotropic attenuation is a potential tool for reservoir characterization. To compensate the Q effects during reverse-time migration (RTM) in viscoacoustic and viscoelastic media, amplitudes need to be compensated during wave propagation; the propagation velocity of the Q-compensated wavefield needs to be the same as in the attenuating wavefield, to restore the phase information. Both amplitude and phase can be compensated when the velocity dispersion and the amplitude loss are decoupled. For wave equations based on the GSLS, because Q effects are coupled in the memory variables, Q-compensated wavefield propagates faster than

Strain fluctuations and elastic constants

Energy Technology Data Exchange (ETDEWEB)

Parrinello, M.; Rahman, A.

1982-03-01

It is shown that the elastic strain fluctuations are a direct measure of elastic compliances in a general anisotropic medium; depending on the ensemble in which the fluctuation is measured either the isothermal or the adiabatic compliances are obtained. These fluctuations can now be calculated in a constant enthalpy and pressure, and hence, constant entropy, ensemble due to recent develpments in the molecular dynamics techniques. A calculation for a Ni single crystal under uniform uniaxial 100 tensile or compressive load is presented as an illustration of the relationships derived between various strain fluctuations and the elastic modulii. The Born stability criteria and the behavior of strain fluctuations are shown to be related.

Evolution of the solar constant

International Nuclear Information System (INIS)

Newman, M.J.

1978-01-01

The ultimate source of the energy utilized by life on Earth is the Sun, and the behavior of the Sun determines to a large extent the conditions under which life originated and continues to thrive. What can be said about the history of the Sun. Has the solar constant, the rate at which energy is received by the Earth from the Sun per unit area per unit time, been constant at its present level since Archean times. Three mechanisms by which it has been suggested that the solar energy output can vary with time are discussed, characterized by long (approx. 10 9 years), intermediate (approx. 10 8 years), and short (approx. years to decades) time scales

Spin-rotation and NMR shielding constants in HCl

Energy Technology Data Exchange (ETDEWEB)

Jaszuński, Michał, E-mail: michal.jaszunski@icho.edu.pl [Institute of Organic Chemistry, Polish Academy of Sciences, 01-224 Warszawa, Kasprzaka 44 (Poland); Repisky, Michal; Demissie, Taye B.; Komorovsky, Stanislav; Malkin, Elena; Ruud, Kenneth [Centre for Theoretical and Computational Chemistry, University of Tromsø—The Arctic University of Norway, N-9037 Tromsø (Norway); Garbacz, Piotr; Jackowski, Karol; Makulski, Włodzimierz [Laboratory of NMR Spectroscopy, Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw (Poland)

2013-12-21

The spin-rotation and nuclear magnetic shielding constants are analysed for both nuclei in the HCl molecule. Nonrelativistic ab initio calculations at the CCSD(T) level of approximation show that it is essential to include relativistic effects to obtain spin-rotation constants consistent with accurate experimental data. Our best estimates for the spin-rotation constants of {sup 1}H{sup 35}Cl are C{sub Cl}  = −53.914 kHz and C{sub H}  = 42.672 kHz (for the lowest rovibrational level). For the chlorine shielding constant, the ab initio value computed including the relativistic corrections, σ(Cl) = 976.202 ppm, provides a new absolute shielding scale; for hydrogen we find σ(H) = 31.403 ppm (both at 300 K). Combining the theoretical results with our new gas-phase NMR experimental data allows us to improve the accuracy of the magnetic dipole moments of both chlorine isotopes. For the hydrogen shielding constant, including relativistic effects yields better agreement between experimental and computed values.

Spin-rotation and NMR shielding constants in HCl

International Nuclear Information System (INIS)

Jaszuński, Michał; Repisky, Michal; Demissie, Taye B.; Komorovsky, Stanislav; Malkin, Elena; Ruud, Kenneth; Garbacz, Piotr; Jackowski, Karol; Makulski, Włodzimierz

2013-01-01

The spin-rotation and nuclear magnetic shielding constants are analysed for both nuclei in the HCl molecule. Nonrelativistic ab initio calculations at the CCSD(T) level of approximation show that it is essential to include relativistic effects to obtain spin-rotation constants consistent with accurate experimental data. Our best estimates for the spin-rotation constants of 1 H 35 Cl are C Cl   = −53.914 kHz and C H   = 42.672 kHz (for the lowest rovibrational level). For the chlorine shielding constant, the ab initio value computed including the relativistic corrections, σ(Cl) = 976.202 ppm, provides a new absolute shielding scale; for hydrogen we find σ(H) = 31.403 ppm (both at 300 K). Combining the theoretical results with our new gas-phase NMR experimental data allows us to improve the accuracy of the magnetic dipole moments of both chlorine isotopes. For the hydrogen shielding constant, including relativistic effects yields better agreement between experimental and computed values

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....

Natural attenuation: A feasible approach to remediation of landfill leachate plumes?

DEFF Research Database (Denmark)

Christensen, Thomas Højlund; Kjeldsen, Peter; Bjerg, Poul Løgstrup

2000-01-01

Natural attenuation has been implemented for petroleum hydrocarbons plumes and recently also for chlorinated solvent plumes, primarily in the USA, but natural attenuation has not yet gained a foothold with respect to leachate plumes. Based on the experiences gained from ten years of research on two...... Danish landfills, it is suggested that natural attenuation is a feasible approach, but much more complicated and demanding than in the case of petroleum hydrocarbons and chlorinated solvent....

Elastic constants from microscopic strain fluctuations

Science.gov (United States)

Sengupta; Nielaba; Rao; Binder

2000-02-01

Fluctuations of the instantaneous local Lagrangian strain epsilon(ij)(r,t), measured with respect to a static "reference" lattice, are used to obtain accurate estimates of the elastic constants of model solids from atomistic computer simulations. The measured strains are systematically coarse-grained by averaging them within subsystems (of size L(b)) of a system (of total size L) in the canonical ensemble. Using a simple finite size scaling theory we predict the behavior of the fluctuations as a function of L(b)/L and extract elastic constants of the system in the thermodynamic limit at nonzero temperature. Our method is simple to implement, efficient, and general enough to be able to handle a wide class of model systems, including those with singular potentials without any essential modification. We illustrate the technique by computing isothermal elastic constants of "hard" and "soft" disk triangular solids in two dimensions from Monte Carlo and molecular dynamics simulations. We compare our results with those from earlier simulations and theory.

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

Derivation of the optical constants of anisotropic

Science.gov (United States)

Aronson, J. R.; Emslie, A. G.; Smith, E. M.; Strong, P. F.

1985-07-01

This report concerns the development of methods for obtaining the optical constants of anisotropic crystals of the triclinic and monoclinic systems. The principal method used, classical dispersion theory, is adapted to these crystal systems by extending the Lorentz line parameters to include the angles characterizing the individual resonances, and by replacing the dielectric constant by a dielectric tensor. The sample crystals are gypsium, orthoclase and chalcanthite. The derived optical constants are shown to be suitable for modeling the optical properties of particulate media in the infrared spectral region. For those materials where suitable size single crystals are not available, an extension of a previously used method is applied to alabaster, a polycrystalline material of the monoclinic crystal system.

Conformally invariant braneworld and the cosmological constant

International Nuclear Information System (INIS)

Guendelman, E.I.

2004-01-01

A six-dimensional braneworld scenario based on a model describing the interaction of gravity, gauge fields and 3+1 branes in a conformally invariant way is described. The action of the model is defined using a measure of integration built of degrees of freedom independent of the metric. There is no need to fine tune any bulk cosmological constant or the tension of the two (in the scenario described here) parallel branes to obtain zero cosmological constant, the only solutions are those with zero 4D cosmological constant. The two extra dimensions are compactified in a 'football' fashion and the branes lie on the two opposite poles of the compact 'football-shaped' sphere

Stability constants of the Europium complexes with the chloride ions; Constantes de estabilidad de los complejos del europio con los iones cloruro

Energy Technology Data Exchange (ETDEWEB)

Jimenez R, M.; Solache R, M.; Rojas H, A. [Instituto Nacional de Investigaciones Nucleares, Departamento de Quimica, A.P. 18-1027, C.P. 11801 Mexico D.F. (Mexico)

2000-07-01

The stability constants of lanthanides complexes with chloride ions which were determined at the same ionic force but in different media, are significantly different. It does not exist a systematic study over these stability constants. The purpose of this work is to determine the stability constants of the europium complexes with chloride ions at 303 K, by the solvents extraction method. (Author)

A stringy nature needs just two constants

International Nuclear Information System (INIS)

Veneziano, G.

1986-01-01

Dual string theories of everything, being purely geometrical, contain only two fundamental constants: c, for relativistic invariance, and a length lambda, for quantization. Planck's and Newton's constants appear only through Planck's length, a ''calculable'' fraction of lambda. Only the existence of a light sector breaks a ''reciprocity'' principle and unification at lambda, which is also the theory's cut-off

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.

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)

GRUCAL, a computer program for calculating macroscopic group constants

International Nuclear Information System (INIS)

Woll, D.

1975-06-01

Nuclear reactor calculations require material- and composition-dependent, energy averaged nuclear data to describe the interaction of neutrons with individual isotopes in material compositions of reactor zones. The code GRUCAL calculates these macroscopic group constants for given compositions from the material-dependent data of the group constant library GRUBA. The instructions for calculating group constants are not fixed in the program, but will be read at the actual execution time from a separate instruction file. This allows to accomodate GRUCAL to various problems or different group constant concepts. (orig.) [de

Attenuation of Self-Generated Tactile Sensations is Predictive, not Postdictive.

Directory of Open Access Journals (Sweden)

2006-01-01

Full Text Available When one finger touches the other, the resulting tactile sensation is perceived as weaker than the same stimulus externally imposed. This attenuation of sensation could result from a predictive process that subtracts the expected sensory consequences of the action, or from a postdictive process that alters the perception of sensations that are judged after the event to be self-generated. In this study we observe attenuation even when the fingers unexpectedly fail to make contact, supporting a predictive process. This predictive attenuation of self-generated sensation may have evolved to enhance the perception of sensations with an external cause.

Attenuation of self-generated tactile sensations is predictive, not postdictive.

Directory of Open Access Journals (Sweden)

Paul M Bays

2006-02-01

Full Text Available When one finger touches the other, the resulting tactile sensation is perceived as weaker than the same stimulus externally imposed. This attenuation of sensation could result from a predictive process that subtracts the expected sensory consequences of the action, or from a postdictive process that alters the perception of sensations that are judged after the event to be self-generated. In this study we observe attenuation even when the fingers unexpectedly fail to make contact, supporting a predictive process. This predictive attenuation of self-generated sensation may have evolved to enhance the perception of sensations with an external cause.

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

Wild type measles virus attenuation independent of type I IFN

Directory of Open Access Journals (Sweden)

Horvat Branka

2008-02-01

Full Text Available Abstract Background Measles virus attenuation has been historically performed by adaptation to cell culture. The current dogma is that attenuated virus strains induce more type I IFN and are more resistant to IFN-induced protection than wild type (wt. Results The adaptation of a measles virus isolate (G954-PBL by 13 passages in Vero cells induced a strong attenuation of this strain in vivo. The adapted virus (G954-V13 differs from its parental strain by only 5 amino acids (4 in P/V/C and 1 in the M gene. While a vaccine strain, Edmonston Zagreb, could replicate equally well in various primate cells, both G954 strains exhibited restriction to the specific cell type used initially for their propagation. Surprisingly, we observed that both G954 strains induced type I IFN, the wt strain inducing even more than the attenuated ones, particularly in human plasmacytoid Dendritic Cells. Type I IFN-induced protection from the infection of both G954 strains depended on the cell type analyzed, being less efficient in the cells used to grow the viral strain. Conclusion Thus, mutations in M and P/V/C proteins can critically affect MV pathogenicity, cellular tropism and lead to virus attenuation without interfering with the α/β IFN system.

Numerical simulation of several impact attenuator design for a formula student car

Science.gov (United States)

Sinaga, Farlian Rizky; Ubaidillah, Kurniawan, Krishna Eka; Fadhil, Muhamad Ivan; Cahyono, Sukmaji Indro; Idris, Muhamad Hafiz

2018-02-01

In the Formula Society of Automotive Engineer (SAE), safety is a vigorous factor. One of the safety components in the Formula SAE car is the impact attenuator. The purpose of this study is to get the impact attenuator design with the best ability to absorb kinetic energy from several existing designs, through numerical approaches, for estimating conditions against dynamic impacts. Material of impact attenuator use combination of aluminum and Zirconium G350. The simulation was caried out by crashing the impact with the rigid wall, to find the deformation that occurs and the energies are absorbed. The impact attenuator design to be simulated should be optimized to meet some parameters in the SAE Formula. The result of impact attenuator simulation should be able to absorb energy of 7350 joules at move 7 m/s and deformation at bulkhead less than 25.4 mm.

Determination of the dissociation constants of some organic complexing agents and stability constants of their uranyl complexes by spectrophotometry

International Nuclear Information System (INIS)

1989-01-01

The dissociation constants of the weak acids derived from quinizarin (1,4-dihydroxy anthraquinone); QMF (2-(2-fury l methyl)), QMPH (2-(2-phenyl methyl)) and QMN (2-(2-naphthyl methyl)) quinizarin were determined. The stability constants of uranyl complexes with the above mentioned ligands were investigated by: 1. The molar-ratio method. 2. Computer program

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.

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

Calculation of magnetic hyperfine constants

International Nuclear Information System (INIS)

Bufaical, R.F.; Maffeo, B.; Brandi, H.S.

1975-01-01

The magnetic hyperfine constants of the V sub(K) center in CaF 2 , SrF 2 and BaF 2 have been calculated assuming a phenomenological model, based on the F 2 - 'central molucule', to describe the wavefunction of the defect. Calculations have shown that introduction of a small degree of covalence, between this central molecule and neighboring ions, is necessary to improve the electronic structure description of the defect. It was also shown that the results for the hyperfine constants are strongly dependent on the relaxations of the ions neighboring the central molecule; these relaxations have been determined by fitting the experimental data. The present results are compared with other previous calculations where similar and different theoretical methods have been used

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.

Implementation of a monitoring protocol for the natural attenuation of soil

International Nuclear Information System (INIS)

Setier, J.C.; Pornain, J.L.; Millette, D.; Perie, F.; Deschenes, L.; Samson, R.

2005-01-01

Large quantities of hydrocarbons are extracted, produced, refined, and transported each year. Despite environmental procedures that are used in industry, the risk of environmental degradation cannot be avoided. Furthermore, aging installations can also present residual contamination. Some of these sites must be decontaminated to residual levels of soil contaminants that are established through discussions with national authorities. These levels are set with respect to the intended use of the site. For several years now, the evaluation of the risk of a contaminant in a particular environment must take into account land use. For certain sites that do not present direct risks for the surrounding environment, natural attenuation offers an interesting alternative to costly remediation strategies. In order to determine whether natural attenuation is a technique suited for soil restoration, TOTAL Exploration Production launched a research project on natural attenuation in 1997. By natural attenuation, we refer to all the processes that act to reduce the concentrations of contaminants in soil (i.e. biotic and abiotic mechanisms). The research project consists of two main components: - The development of decision-making tools designed to evaluate the potential for natural attenuation of hydrocarbons. These software programs, named SITE I and SITE II and developed by the Industrial Chair in Site Remediation and Management of the Ecole Polytechnique de Montreal take into account microbial and biotic processes involved the natural attenuation of contaminants in groundwater (SITE I) and soil (SITE II). - The set-up of a pilot-scale demonstration of natural attenuation in soils within the vadose zone at a refinery belonging to the TOTAL group. This pilot project, done in collaboration with the NSERC Industrial Chair in Site Remediation and Management of the Ecole Polytechnique de Montreal, has the following objectives : 1. Evaluation of the feasibility of natural attenuation as

Novel Intriguing Strategies Attenuating to Sarcopenia

Directory of Open Access Journals (Sweden)

Kunihiro Sakuma

2012-01-01

Full Text Available Sarcopenia, the age-related loss of skeletal muscle mass, is characterized by a deterioration of muscle quantity and quality leading to a gradual slowing of movement, a decline in strength and power, increased risk of fall-related injury, and, often, frailty. Since sarcopenia is largely attributed to various molecular mediators affecting fiber size, mitochondrial homeostasis, and apoptosis, the mechanisms responsible for these deleterious changes present numerous therapeutic targets for drug discovery. Resistance training combined with amino acid-containing supplements is often utilized to prevent age-related muscle wasting and weakness. In this review, we summarize more recent therapeutic strategies (myostatin or proteasome inhibition, supplementation with eicosapentaenoic acid (EPA or ursolic acid, etc. for counteracting sarcopenia. Myostatin inhibitor is the most advanced research with a Phase I/II trial in muscular dystrophy but does not try the possibility for attenuating sarcopenia. EPA and ursolic acid seem to be effective as therapeutic agents, because they attenuate the degenerative symptoms of muscular dystrophy and cachexic muscle. The activation of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α in skeletal muscle by exercise and/or unknown supplementation would be an intriguing approach to attenuating sarcopenia. In contrast, muscle loss with age may not be influenced positively by treatment with a proteasome inhibitor or antioxidant.

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.

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.

Effective x-ray attenuation measurements with full field digital mammography

International Nuclear Information System (INIS)

Heine, John J.; Behera, Madhusmita

2006-01-01

This work shows that effective x-ray attenuation coefficients may be estimated by applying Beer's Law to phantom image data acquired with the General Electric Senographe 2000D full field digital mammography system. Theoretical developments are provided indicating that an approximate form of the Beer's relation holds for polychromatic x-ray beams. The theoretical values were compared with experimentally determined measured values, which were estimated at various detector locations. The measured effective attenuation coefficients are in agreement with those estimated with theoretical developments and numerical integration. The work shows that the measured quantities show little spatial variation. The main ideas are demonstrated with polymethylmethacrylate and breast tissue equivalent phantom imaging experiments. The work suggests that the effective attenuation coefficients may be used as known values for radiometric standardization applications that compensate for the image acquisition influences. The work indicates that it is possible to make quantitative attenuation coefficient measurements from a system designed for clinical purposes

Vanishing cosmological constant in elementary particles theory

International Nuclear Information System (INIS)

Pisano, F.; Tonasse, M.D.

1997-01-01

The quest of a vanishing cosmological constant is considered in the simplest anomaly-free chiral gauge extension of the electroweak standard model where the new physics is limited to a well defined additional flavordynamics above the Fermi scale, namely up to a few TeVs by matching the gauge coupling constants at the electroweak scale, and with an extended Higgs structure. In contrast to the electroweak standard model, it is shown how the extended scalar sector of the theory allows a vanishing or a very small cosmological constant. the details of the cancellation mechanism are presented. At accessible energies the theory is indistinguishable from the standard model of elementary particles and it is in agreement with all existing data. (author). 32 refs

Determination of constants of factorized pairing force from conservation laws

International Nuclear Information System (INIS)

Voronkov, Yu.P.; Mikhajlov, V.M.

1975-01-01

The constants of a factorized interaction in the particle-particle channel are evaluated on the basis of average field parameters and Cooper pairing. The relations between the constants of multipole particle-particle forces are derived for the spherical nuclei. The constants of the quadrupole pairing are obtained for deformed nuclei from the angular momentum conservation law. The calculated constants are compared with empiricalones

Enhanced Attenuation: Chlorinated Organics

Science.gov (United States)

2008-04-01

attenuation capacity of the aquifer downgradient from the source (e.g., permeable reactive barriers or phytoremediation ) Selection of EA remedies should be...prevalence and/or mobility of nitrate and sulfate compounds and/or metals such as iron, manganese, chromium, copper, and arsenic . Furthermore, in...ranging from very aggressive source destruction and removal methods to less energy-intensive methods, such as phytoremediation . In many cases, it

Measurement of attenuation coefficients of the fundamental and second harmonic waves in water

Science.gov (United States)

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

2016-02-01

Attenuation corrections in nonlinear acoustics play an important role in the study of nonlinear fluids, biomedical imaging, or solid material characterization. The measurement of attenuation coefficients in a nonlinear regime is not easy because they depend on the source pressure and requires accurate diffraction corrections. In this work, the attenuation coefficients of the fundamental and second harmonic waves which come from the absorption of water are measured in nonlinear ultrasonic experiments. Based on the quasilinear theory of the KZK equation, the nonlinear sound field equations are derived and the diffraction correction terms are extracted. The measured sound pressure amplitudes are adjusted first for diffraction corrections in order to reduce the impact on the measurement of attenuation coefficients from diffractions. The attenuation coefficients of the fundamental and second harmonics are calculated precisely from a nonlinear least squares curve-fitting process of the experiment data. The results show that attenuation coefficients in a nonlinear condition depend on both frequency and source pressure, which are much different from a linear regime. In a relatively lower drive pressure, the attenuation coefficients increase linearly with frequency. However, they present the characteristic of nonlinear growth in a high drive pressure. As the diffraction corrections are obtained based on the quasilinear theory, it is important to use an appropriate source pressure for accurate attenuation measurements.

Evaluation of downwelling diffuse attenuation coefficient algorithms in the Red Sea

KAUST Repository

Tiwari, Surya Prakash; Yellepeddi, Sarma B.; Jones, Burton

2016-01-01

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

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.

On determining dose rate constants spectroscopically

International Nuclear Information System (INIS)

Rodriguez, M.; Rogers, D. W. O.

2013-01-01

Purpose: To investigate several aspects of the Chen and Nath spectroscopic method of determining the dose rate constants of 125 I and 103 Pd seeds [Z. Chen and R. Nath, Phys. Med. Biol. 55, 6089–6104 (2010)] including the accuracy of using a line or dual-point source approximation as done in their method, and the accuracy of ignoring the effects of the scattered photons in the spectra. Additionally, the authors investigate the accuracy of the literature's many different spectra for bare, i.e., unencapsulated 125 I and 103 Pd sources. Methods: Spectra generated by 14 125 I and 6 103 Pd seeds were calculated in vacuo at 10 cm from the source in a 2.7 × 2.7 × 0.05 cm 3 voxel using the EGSnrc BrachyDose Monte Carlo code. Calculated spectra used the initial photon spectra recommended by AAPM's TG-43U1 and NCRP (National Council of Radiation Protection and Measurements) Report 58 for the 125 I seeds, or TG-43U1 and NNDC(2000) (National Nuclear Data Center, 2000) for 103 Pd seeds. The emitted spectra were treated as coming from a line or dual-point source in a Monte Carlo simulation to calculate the dose rate constant. The TG-43U1 definition of the dose rate constant was used. These calculations were performed using the full spectrum including scattered photons or using only the main peaks in the spectrum as done experimentally. Statistical uncertainties on the air kerma/history and the dose rate/history were ⩽0.2%. The dose rate constants were also calculated using Monte Carlo simulations of the full seed model. Results: The ratio of the intensity of the 31 keV line relative to that of the main peak in 125 I spectra is, on average, 6.8% higher when calculated with the NCRP Report 58 initial spectrum vs that calculated with TG-43U1 initial spectrum. The 103 Pd spectra exhibit an average 6.2% decrease in the 22.9 keV line relative to the main peak when calculated with the TG-43U1 rather than the NNDC(2000) initial spectrum. The measured values from three different

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.

Ultrasonic attenuation of CdSe at low temperatures

Energy Technology Data Exchange (ETDEWEB)

Fernandez, B.J., E-mail: braulio@ula.v [Centro de Estudios de Semiconductores, Departamento de Fisica, Facultad de Ciencias, Universidad de Los Andes Apartado de Correos No.1, La Hechicera, Merida 5251 (Venezuela, Bolivarian Republic of); Calderon, E.; Bracho, D.B. [Centro de Estudios de Semiconductores, Departamento de Fisica, Facultad de Ciencias, Universidad de Los Andes Apartado de Correos No.1, La Hechicera, Merida 5251 (Venezuela, Bolivarian Republic of); Perez, J.F. [Laboratorio de Instrumentacion Cientifica, Facultad de Ciencias, Universidad de Los Andes Apartado de Correos No.1, La Hechicera, Merida 5251 (Venezuela, Bolivarian Republic of)

2010-08-01

The ultrasonic attenuation of a single crystal of CdSe has been investigated over the temperature range from 1.2 to 300 K at frequencies of 10, 30 and 90 MHz. We report here the temperature dependence of the attenuation in the range 1.2-30 K for piezoactive and non-piezoactive acoustic waves. A temperature-induced relaxation for two piezoactive waves, which scale with frequency towards higher temperatures, was found. A modified Hutson and White model with a new parameter {gamma} is proposed to explain the relaxation maxima of our data and others in the literature. In this model the parameter {gamma}, which seems to be closely related to the compensation, takes into account the impurities-sound wave piezoelectric coupling. By inverting the proposed expression for the sound attenuation to obtain the electrical conductivity from the relaxation, it is found that impurity conductivity of the hopping type is the dominant conduction process at low temperatures.

Ultrasonic attenuation of CdSe at low temperatures

International Nuclear Information System (INIS)

Fernandez, B.J.; Calderon, E.; Bracho, D.B.; Perez, J.F.

2010-01-01

The ultrasonic attenuation of a single crystal of CdSe has been investigated over the temperature range from 1.2 to 300 K at frequencies of 10, 30 and 90 MHz. We report here the temperature dependence of the attenuation in the range 1.2-30 K for piezoactive and non-piezoactive acoustic waves. A temperature-induced relaxation for two piezoactive waves, which scale with frequency towards higher temperatures, was found. A modified Hutson and White model with a new parameter γ is proposed to explain the relaxation maxima of our data and others in the literature. In this model the parameter γ, which seems to be closely related to the compensation, takes into account the impurities-sound wave piezoelectric coupling. By inverting the proposed expression for the sound attenuation to obtain the electrical conductivity from the relaxation, it is found that impurity conductivity of the hopping type is the dominant conduction process at low temperatures.

Plasmodium yoelii: induction of attenuated mutants by irradiation

International Nuclear Information System (INIS)

Waki, S.; Yonome, I.; Suzuki, M.

1986-01-01

When erythrocytic forms of Plasmodium yoelii nigeriensis, which is invariably fatal in mice, were exposed to X rays, the dose to reduce surviving parasites to one millionth was 100 gray (10 Krad). A suspension of 5 X 10(6) per ml of parasitized erythrocyte was irradiated at 100 gray, and 0.2 ml aliquots were inoculated into 22 mice. Eleven mice showed patent parasitemia, and in these the growth curves were less steep than that found in nonirradiated parasites. The infections of 8 mice of the 11 were self-resolving, and the attenuated feature of the parasites maintained following a limited number of blood passages. The parasites were slowly growing even in nude mice and cause self-resolving infections in intact mice. BALB/c mice immunized with the attenuated parasites were protected against subsequent challenge infections with the original virulent erythrocytic and sporogonic forms. These findings indicate that attenuated mutants of malaria parasites can be readily induced by this method

Intensity attenuation relation at Chamba–Garhwal area in north-west ...

Indian Academy of Sciences (India)

Seismic hazard assessment of any region depends on the attenuation relation ... The present study includes 10 moderate and major earthquakes (Ms ≥ 4.9) that had occurred during the ... city and attenuation of strong seismic ground motion. ... Seismologists have benefitted from the development .... In that case, we inferred.

Compact plasmonic variable optical attenuator

DEFF Research Database (Denmark)

Leosson, Kristjan; Rosenzveig, Tiberiu; Hermannsson, Pétur Gordon

2008-01-01

We demonstrate plasmonic nanowire-based thermo-optic variable optical attenuators operating in the 1525-1625 nm wavelength range. The devices have a footprint as low as 1 mm, extinction ratio exceeding 40 dB, driving voltage below 3 V, and full modulation bandwidth of 1 kHz. The polarization...

A systematic evaluation of the dose-rate constant determined by photon spectrometry for 21 different models of low-energy photon-emitting brachytherapy sources.

Science.gov (United States)

Chen, Zhe Jay; Nath, Ravinder

2010-10-21

The aim of this study was to perform a systematic comparison of the dose-rate constant (Λ) determined by the photon spectrometry technique (PST) with the consensus value ((CON)Λ) recommended by the American Association of Physicists in Medicine (AAPM) for 21 low-energy photon-emitting interstitial brachytherapy sources. A total of 63 interstitial brachytherapy sources (21 different models with 3 sources per model) containing either (125)I (14 models), (103)Pd (6 models) or (131)Cs (1 model) were included in this study. A PST described by Chen and Nath (2007 Med. Phys. 34 1412-30) was used to determine the dose-rate constant ((PST)Λ) for each source model. Source-dependent variations in (PST)Λ were analyzed systematically against the spectral characteristics of the emitted photons and the consensus values recommended by the AAPM brachytherapy subcommittee. The values of (PST)Λ for the encapsulated sources of (103)Pd, (125)I and (131)Cs varied from 0.661 to 0.678 cGyh(-1) U(-1), 0.959 to 1.024 cGyh(-1)U(-1) and 1.066 to 1.073 cGyh(-1)U(-1), respectively. The relative variation in (PST)Λ among the six (103)Pd source models, caused by variations in photon attenuation and in spatial distributions of radioactivity among the source models, was less than 3%. Greater variations in (PST)Λ were observed among the 14 (125)I source models; the maximum relative difference was over 6%. These variations were caused primarily by the presence of silver in some (125)I source models and, to a lesser degree, by the variations in photon attenuation and in spatial distribution of radioactivity among the source models. The presence of silver generates additional fluorescent x-rays with lower photon energies which caused the (PST)Λ value to vary from 0.959 to 1.019 cGyh(-1)U(-1) depending on the amount of silver used by a given source model. For those (125)I sources that contain no silver, their (PST)Λ was less variable and had values within 1% of 1.024 cGyh(-1)U(-1). For the 16

Derivation of linear attenuation coefficients from CT numbers for low-energy photons

International Nuclear Information System (INIS)

Watanabe, Y.

1999-01-01

One can estimate photon attenuation properties from the CT number. In a standard method one assumes that the linear attenuation coefficient is proportional to electron density and ignores its nonlinear dependence on atomic number. When the photon energy is lower than about 50 keV, such as for brachytherapy applications, however, photoelectric absorption and Rayleigh scattering become important. Hence the atomic number must be explicitly considered in estimating the linear attenuation coefficient. In this study we propose a method to more accurately estimate the linear attenuation coefficient of low-energy photons from CT numbers. We formulate an equation that relates the CT number to the electron density and the effective atomic number. We use a CT calibration phantom to determine unknown coefficients in the equation. The equation with a given CT number is then solved for the effective atomic number, which in turn is used to calculate the linear attenuation coefficient for low-energy photons. We use the CT phantom to test the new method. The method significantly improves the standard method in estimating the attenuation coefficient at low photon energies (20keV≤E≤40keV) for materials with high atomic numbers. (author)

Oesophagostomum columbianum : immunization of young lambs using gamma ray attenuated inefective larvae

International Nuclear Information System (INIS)

Sharma, R.L.; Dhar, D.N.

1987-01-01

Infective Oesophagostomum columbianum larvae were successfully attenuated by exposing them to a gamma radiation dose levels of either 40 or 50 Krad. Lambs receiving a single vaccination dose of 2000 infective larvae attenuated at 40 Krad developed partial protection, whereas those vaccinated with similar dose of infection with 50 Krad irradiated larvae failed to develop any protection. A double vaccination schedule comprising of 500 and 2000 gamma attenuated (40 Krad) infective larvae induced a significantly higher level of protection against the challenge dose. The possible use of radiation attenuated larvae as vaccine for immunoprophylaxis against ovine Oesophagostomiasis has been discussed. (author). 11 refs., 2 tables

Lattice constant measurement from electron backscatter diffraction patterns

DEFF Research Database (Denmark)

Saowadee, Nath; Agersted, Karsten; Bowen, Jacob R.

2017-01-01

Kikuchi bands in election backscattered diffraction patterns (EBSP) contain information about lattice constants of crystallographic samples that can be extracted via the Bragg equation. An advantage of lattice constant measurement from EBSPs over diffraction (XRD) is the ability to perform local ...

Towards Grothendieck constants and LHV models in quantum mechanics

International Nuclear Information System (INIS)

Hua, Bobo; Li, Ming; Zhang, Tinggui; Zhou, Chunqin; Li-Jost, Xianqing; Fei, Shao-Ming

2015-01-01

We adopt a continuous model to estimate the Grothendieck constants. An analytical formula to compute the lower bounds of Grothendieck constants has been explicitly derived for arbitrary orders, which improves previous bounds. Moreover, our lower bound of the Grothendieck constant of order three gives a refined bound of the threshold value for the nonlocality of the two-qubit Werner states. (paper)

Beauty vector meson decay constants from QCD sum rules

Energy Technology Data Exchange (ETDEWEB)

Lucha, Wolfgang [Institute for High Energy Physics, Austrian Academy of Sciences, Nikolsdorfergasse 18, A-1050 Vienna (Austria); Melikhov, Dmitri [Institute for High Energy Physics, Austrian Academy of Sciences, Nikolsdorfergasse 18, A-1050 Vienna (Austria); D. V. Skobeltsyn Institute of Nuclear Physics, M. V. Lomonosov Moscow State University, 119991, Moscow (Russian Federation); Simula, Silvano [Istituto Nazionale di Fisica Nucleare, Sezione di Roma Tre, Via della Vasca Navale 84, I-00146, Roma (Italy)

2016-01-22

We present the outcomes of a very recent investigation of the decay constants of nonstrange and strange heavy-light beauty vector mesons, with special emphasis on the ratio of any such decay constant to the decay constant of the corresponding pseudoscalar meson, by means of Borel-transformed QCD sum rules. Our results suggest that both these ratios are below unity.

Inverse problem in anisotropic poroelasticity: drained constants from undrained ultrasound measurements.

Science.gov (United States)

Berryman, James G; Nakagawa, Seiji

2010-02-01

Poroelastic analysis has traditionally focused on the relationship between dry and drained constants, which are assumed known, and the saturated or undrained constants, which are assumed unknown. However, there are many applications in this field of study for which the main measurements can only be made on the saturated/undrained system, and then it is uncertain what the effects of the fluids were on the system, since the drained constants remain a mystery. The work presented here shows how to deduce drained constants from undrained constants for anisotropic systems having symmetries ranging from isotropic to orthotropic. Laboratory ultrasound data are then inverted for the drained constants in three granular packings: one of glass beads, and two others for distinct types of more or less angular sand grain packings. Experiments were performed under uniaxial stress, which resulted in hexagonal (transversely isotropic) symmetry of the poroelastic response. One important conclusion from the general analysis is that the drained constants are uniquely related to the undrained constants, assuming that porosity, grain bulk modulus, and pore fluid bulk modulus are already known. Since the resulting system of equations for all the drained constants is linear, measurement error in undrained constants also propagates linearly into the computed drained constants.

Inverse problem in anisotropic poroelasticity: Drained constants from undrained ultrasound measurements

Energy Technology Data Exchange (ETDEWEB)

Berryman, J.G.; Nakagawa, S.

2009-11-20

Poroelastic analysis has traditionally focused on the relationship between dry or drained constants which are assumed known and the saturated or undrained constants which are assumed unknown. However, there are many applications in this field of study for which the main measurements can only be made on the saturated/undrained system, and then it is uncertain what the eects of the uids were on the system, since the drained constants remain a mystery. The work presented here shows how to deduce drained constants from undrained constants for anisotropic systems having symmetries ranging from isotropic to orthotropic. Laboratory ultrasound data are then inverted for the drained constants in three granular packings: one of glass beads, and two others for distinct types of more or less angular sand grain packings. Experiments were performed under uniaxial stress, which resulted in hexagonal (transversely isotropic) symmetry of the poroelastic response. One important conclusion from the general analysis is that the drained constants are uniquely related to the undrained constants, assuming that porosity, grain bulk modulus, and pore uid bulk modulus are already known. Since the resulting system of equations for all the drained constants is linear, measurement error in undrained constants also propagates linearly into the computed drained constants.

Optimal trace inequality constants for interior penalty discontinuous Galerkin discretisations of elliptic operators using arbitrary elements with non-constant Jacobians

Science.gov (United States)

Owens, A. R.; Kópházi, J.; Eaton, M. D.

2017-12-01

In this paper, a new method to numerically calculate the trace inequality constants, which arise in the calculation of penalty parameters for interior penalty discretisations of elliptic operators, is presented. These constants are provably optimal for the inequality of interest. As their calculation is based on the solution of a generalised eigenvalue problem involving the volumetric and face stiffness matrices, the method is applicable to any element type for which these matrices can be calculated, including standard finite elements and the non-uniform rational B-splines of isogeometric analysis. In particular, the presented method does not require the Jacobian of the element to be constant, and so can be applied to a much wider variety of element shapes than are currently available in the literature. Numerical results are presented for a variety of finite element and isogeometric cases. When the Jacobian is constant, it is demonstrated that the new method produces lower penalty parameters than existing methods in the literature in all cases, which translates directly into savings in the solution time of the resulting linear system. When the Jacobian is not constant, it is shown that the naive application of existing approaches can result in penalty parameters that do not guarantee coercivity of the bilinear form, and by extension, the stability of the solution. The method of manufactured solutions is applied to a model reaction-diffusion equation with a range of parameters, and it is found that using penalty parameters based on the new trace inequality constants result in better conditioned linear systems, which can be solved approximately 11% faster than those produced by the methods from the literature.

Nuclei quadrupole coupling constants in diatomic molecule

International Nuclear Information System (INIS)

Ivanov, A.I.; Rebane, T.K.

1993-01-01

An approximate relationship between the constants of quadrupole interaction of nuclei in a two-atom molecule is found. It enabled to establish proportionality of oscillatory-rotation corrections to these constants for both nuclei in the molecule. Similar results were obtained for the factors of electrical dipole-quadrupole screening of nuclei. Applicability of these relationships is proven by the example of lithium deuteride molecule. 4 refs., 1 tab

Photon attenuation properties of some thorium, uranium and plutonium compounds

Energy Technology Data Exchange (ETDEWEB)

Singh, V. P.; Badiger, N. M. [Karnatak University, Department of Physics, Dharwad-580003, Karnataka (India); Vega C, H. R., E-mail: kudphyvps@rediffmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas, Zac. (Mexico)

2015-10-15

Mass attenuation coefficients, effective atomic numbers, effective electron densities for nuclear materials; thorium, uranium and plutonium compounds have been studied. The photon attenuation properties for the compounds have been investigated for partial photon interaction processes by photoelectric effect, Compton scattering and pair production. The values of these parameters have been found to change with photon energy and interaction process. The variations of mass attenuation coefficients, effective atomic number and electron density with energy are shown graphically. Moreover, results have shown that these compounds are better shielding and suggesting smaller dimensions. The study would be useful for applications of these materials for gamma ray shielding requirement. (Author)

Fast neutron attenuation measurements for detection of illicit materials

International Nuclear Information System (INIS)

Lee, Hee Seock; Chung, Chin Wha; Guon, Ki Il; Lee, Bo Young; Ko, Seung Kook; Shin, Yong Mu

2002-01-01

Experiments were carried out to develop a novel method using neutron attenuation for the detection of illicit materials. By using pulsed fast neutrons generated from a Bi target bombarded with a 2 GeV electron beam, attenuation spectra of C, N, and O have been measured to study the feasibility of a practical application. The spectral dependence on the material thickness and the geometrical distribution as well as the ability to identify different elements in a layered environment have been studied. For the elements mentioned here, the total cross sections have been obtained from the measured attenuation spectra and compared with ENDF-VI, which showed good agreement. The study confirms that a conventional low energy electron linac can be put into a practical use, and some practical idea is presented

Non-minimally coupled varying constants quantum cosmologies

International Nuclear Information System (INIS)

Balcerzak, Adam

2015-01-01

We consider gravity theory with varying speed of light and varying gravitational constant. Both constants are represented by non-minimally coupled scalar fields. We examine the cosmological evolution in the near curvature singularity regime. We find that at the curvature singularity the speed of light goes to infinity while the gravitational constant vanishes. This corresponds to the Newton's Mechanics limit represented by one of the vertex of the Bronshtein-Zelmanov-Okun cube [1,2]. The cosmological evolution includes both the pre-big-bang and post-big-bang phases separated by the curvature singularity. We also investigate the quantum counterpart of the considered theory and find the probability of transition of the universe from the collapsing pre-big-bang phase to the expanding post-big-bang phase

Effects of quantum entropy on bag constant

International Nuclear Information System (INIS)

Miller, D.E.; Tawfik, A.

2012-01-01

The effects of quantum entropy on the bag constant are studied at low temperatures and for small chemical potentials. The inclusion of the quantum entropy of the quarks in the equation of state provides the hadronic bag with an additional heat which causes a decrease in the effective latent heat inside the bag. We have considered two types of baryonic bags, Δ and Ω - . In both cases we have found that the bag constant without the quantum entropy almost does not change with temperature and quark chemical potential. The contribution from the quantum entropy to the equation of state clearly decreases the value of the bag constant. Furthermore, we construct states densities for quarks using the 'Thomas Fermi model' and take into consideration a thermal potential for the interaction. (author)

Transport equivalent diffusion constants for reflector region in PWRs

International Nuclear Information System (INIS)

Tahara, Yoshihisa; Sekimoto, Hiroshi

2002-01-01

The diffusion-theory-based nodal method is widely used in PWR core designs for reason of its high computing speed in three-dimensional calculations. The baffle/reflector (B/R) constants used in nodal calculations are usually calculated based on a one-dimensional transport calculation. However, to achieve high accuracy of assembly power prediction, two-dimensional model is needed. For this reason, the method for calculating transport equivalent diffusion constants of reflector material was developed so that the neutron currents on the material boundaries could be calculated exactly in diffusion calculations. Two-dimensional B/R constants were calculated using the transport equivalent diffusion constants in the two-dimensional diffusion calculation whose geometry reflected the actual material configuration in the reflector region. The two-dimensional B/R constants enabled us to predict assembly power within an error of 1.5% at hot full power conditions. (author)

Time variable cosmological constants from the age of universe

International Nuclear Information System (INIS)

Xu Lixin; Lu Jianbo; Li Wenbo

2010-01-01

In this Letter, time variable cosmological constant, dubbed age cosmological constant, is investigated motivated by the fact: any cosmological length scale and time scale can introduce a cosmological constant or vacuum energy density into Einstein's theory. The age cosmological constant takes the form ρ Λ =3c 2 M P 2 /t Λ 2 , where t Λ is the age or conformal age of our universe. The effective equation of state (EoS) of age cosmological constant are w Λ eff =-1+2/3 (√(Ω Λ ))/c and w Λ eff =-1+2/3 (√(Ω Λ ))/c (1+z) when the age and conformal age of universe are taken as the role of cosmological time scales respectively. The EoS are the same as the so-called agegraphic dark energy models. However, the evolution histories are different from the agegraphic ones for their different evolution equations.

Seed viability constants for Eucalyptus grandis Constantes de viabilidade para sementes de Eucalyptus grandis

Directory of Open Access Journals (Sweden)

Jussara Bertho Fantinatti

2007-01-01

Full Text Available This work aimed to analyse Eucalyptus grandis W.Hill ex Maiden seed behaviour, under controlled deterioration, and to estimate viability equation constants for the species. Seeds were harvested in the growing season of 1999, and the moisture contents were adjusted from 11.3% to a range between 1.2 and 18.1% at 25ºC. The subsamples were sealed into laminate aluminium-foil packets, for storage in incubators at 40, 50 and 65±0.5ºC. The seeds presented orthodox performance, in which the constants for predicting seed longevity of E. grandis were K E = 9.661, C W = 6.467, C H = 0.03498 and C Q = 0.0002330. The usual and inverse relationship between water content and seed longevity was also observed. The lowest moisture content limit for application of the viability equation at 65ºC was 4.9%, estimated under hygroscopic equilibrium with 23% of relative humidity in the storage environment.Este trabalho teve como objetivos verificar o desempenho de sementes de Eucalyptus grandis W.Hill ex Maiden, após a deterioração em condições controladas, e obter as constantes da equação de viabilidade. As sementes foram colhidas na safra de 1999, e a umidade foi ajustada de 11,3% para valores entre 1,2 e 18,1% a 25ºC As subamostras foram acondicionadas em embalagens de alumínio termossoldadas, armazenadas a 40, 50 e 65±0,5ºC. As sementes apresentaram um desempenho ortodoxo em relação ao armazenamento. As constantes para a predição da longevidade foram K E = 9,661, C W = 6,467, C H = 0,03498 e C Q = 0,0002330. Foi observada a relação inversa entre teor de água e longevidade. O limite inferior de grau de umidade, calculado para aplicação da equação a 65ºC, foi de 4,9%, estimativa obtida sob equilíbrio higroscópico com umidade relativa de 23% no ambiente de armazenamento.

Multiple-energy tissue-cancellation applications of a digital beam attenuator to chest radiography

International Nuclear Information System (INIS)

Dobbins, J.T. III.

1985-01-01

The digitally-formed primary beam attenuator (DBA) spatially modulates the x-ray fluence incident upon the patient to selectively attenuate regions of interest. The DBA attenuating mask is constructed from CeO 2 powder by a modified printing technique and uses image information from an initial low-dose exposure. Two tissue-cancellation imaging techniques are investigated with the DBA: (1) energy-dependent information is used to form a beam attenuator that attenuates specific tissues in the primary x-ray beam for tissue-cancelled film radiography; (2) the beam attenuator is used to improve image signal-to-noise and scattered radiation properties in traditional energy-subtraction tissue-cancellation imaging with digital detectors. The tissue-cancellation techniques in the primary x-ray beam were capable of adequately removing either soft-tissue or bone from the final compensated film radiograph when using a phantom with well defined soft-tissue and bone sections. However, when tried on an anthropomorphic chest phantom the results were adequate for cancellation of large soft tissue structures, but unsatisfactory for cancellation of bony structures such as the ribs, because of the limited spatial frequency content of the attenuating mask. The second technique (with digital detectors) showed improved uniformity of image signal-to-noise and a two-fold increase in soft-tissue nodule contrast due to improved scattered radiation properties. The tissue-cancelled images contained residual image contributions from the presence of the attenuating mask, but this residual may be correctable by future algorithms

Determination of Henry's constant, the dissociation constant, and the buffer capacity of the bicarbonate system in ruminal fluid.

Science.gov (United States)

Hille, Katharina T; Hetz, Stefan K; Rosendahl, Julia; Braun, Hannah-Sophie; Pieper, Robert; Stumpff, Friederike

2016-01-01

Despite the clinical importance of ruminal acidosis, ruminal buffering continues to be poorly understood. In particular, the constants for the dissociation of H2CO3 and the solubility of CO2 (Henry's constant) have never been stringently determined for ruminal fluid. The pH was measured in parallel directly in the rumen and the reticulum in vivo, and in samples obtained via aspiration from 10 fistulated cows on hay- or concentrate-based diets. The equilibrium constants of the bicarbonate system were measured at 38°C both using the Astrup technique and a newly developed method with titration at 2 levels of partial pressure of CO2 (pCO2; 4.75 and 94.98 kPa), yielding mean values of 0.234 ± 0.005 mmol ∙ L(-1) ∙ kPa(-1) and 6.11 ± 0.02 for Henry's constant and the dissociation constant, respectively (n/n = 31/10). Both reticular pH and the pH of samples measured after removal were more alkalic than those measured in vivo in the rumen (by ΔpH = 0.87 ± 0.04 and 0.26 ± 0.04). The amount of acid or base required to shift the pH of ruminal samples to 6.4 or 5.8 (base excess) differed between the 2 feeding groups. Experimental results are compared with the mathematical predictions of an open 2-buffer Henderson-Hasselbalch equilibrium model. Because pCO2 has pronounced effects on ruminal pH and can decrease rapidly in samples removed from the rumen, introduction of a generally accepted protocol for determining the acid-base status of ruminal fluid with standard levels of pCO2 and measurement of base excess in addition to pH should be considered. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

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

On Riemannian manifolds (Mn, g) of quasi-constant curvature

International Nuclear Information System (INIS)

Rahman, M.S.

1995-07-01

A Riemannian manifold (M n , g) of quasi-constant curvature is defined. It is shown that an (M n , g) in association with other class of manifolds gives rise, under certain conditions, to a manifold of quasi-constant curvature. Some observations on how a manifold of quasi-constant curvature accounts for a pseudo Ricci-symmetric manifold and quasi-umbilical hypersurface are made. (author). 10 refs

analysis of rain rate and rain attenuation for earth-space

African Journals Online (AJOL)

Rain rate and rain attenuation predictions are vital when designing microwave satellite and terrestrial communication links, such as in the Ku and Ka bands. This paper presents the cumulative distribution functions (CDFs) of the predicted rain rate and rain attenuation for Uyo, Akwa Ibom State (AKS) (Latitude: 4.88°N, ...

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.

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.

Evaluation of attenuating materials: model for the distribution of scattered radiation

International Nuclear Information System (INIS)

Costa, Paulo R.

1996-01-01

A mathematical model for the behaviour of the distribution of photon scattered by attenuating media is presented. Shielding barriers or attenuating materials used in tests of quality control in radiology are proposed. Comparative results for Lucite are reported

Chandra Independently Determines Hubble Constant

Science.gov (United States)

2006-08-01

A critically important number that specifies the expansion rate of the Universe, the so-called Hubble constant, has been independently determined using NASA's Chandra X-ray Observatory. This new value matches recent measurements using other methods and extends their validity to greater distances, thus allowing astronomers to probe earlier epochs in the evolution of the Universe. "The reason this result is so significant is that we need the Hubble constant to tell us the size of the Universe, its age, and how much matter it contains," said Max Bonamente from the University of Alabama in Huntsville and NASA's Marshall Space Flight Center (MSFC) in Huntsville, Ala., lead author on the paper describing the results. "Astronomers absolutely need to trust this number because we use it for countless calculations." Illustration of Sunyaev-Zeldovich Effect Illustration of Sunyaev-Zeldovich Effect The Hubble constant is calculated by measuring the speed at which objects are moving away from us and dividing by their distance. Most of the previous attempts to determine the Hubble constant have involved using a multi-step, or distance ladder, approach in which the distance to nearby galaxies is used as the basis for determining greater distances. The most common approach has been to use a well-studied type of pulsating star known as a Cepheid variable, in conjunction with more distant supernovae to trace distances across the Universe. Scientists using this method and observations from the Hubble Space Telescope were able to measure the Hubble constant to within 10%. However, only independent checks would give them the confidence they desired, considering that much of our understanding of the Universe hangs in the balance. Chandra X-ray Image of MACS J1149.5+223 Chandra X-ray Image of MACS J1149.5+223 By combining X-ray data from Chandra with radio observations of galaxy clusters, the team determined the distances to 38 galaxy clusters ranging from 1.4 billion to 9.3 billion

On the attenuation of x-rays and gamma-rays in dilute solutions

DEFF Research Database (Denmark)

Gerward, Leif

1996-01-01

The theory of X-ray and gamma-ray attenuation in solutions is developed. The rule of mixture for the calculation of mass and linear attenuation coefficients is elaborated in the general case as well as in the limit of extreme dilution. The validity of the latter approximation is illustrated...... by the attenuation of 17.443 keV X-rays in aqueous solutions of NaCl. Copyright (C) 1996 Elsevier Science Ltd...

MR-based attenuation correction for cardiac FDG PET on a hybrid PET/MRI scanner: comparison with standard CT attenuation correction

Energy Technology Data Exchange (ETDEWEB)

Vontobel, Jan; Liga, Riccardo; Possner, Mathias; Clerc, Olivier F.; Mikulicic, Fran; Veit-Haibach, Patrick; Voert, Edwin E.G.W. ter; Fuchs, Tobias A.; Stehli, Julia; Pazhenkottil, Aju P.; Benz, Dominik C.; Graeni, Christoph; Gaemperli, Oliver; Herzog, Bernhard; Buechel, Ronny R.; Kaufmann, Philipp A. [University Hospital Zurich, Department of Nuclear Medicine, Zurich (Switzerland)

2015-09-15

The aim of this study was to evaluate the feasibility of attenuation correction (AC) for cardiac {sup 18}F-labelled fluorodeoxyglucose (FDG) positron emission tomography (PET) using MR-based attenuation maps. We included 23 patients with no known cardiac history undergoing whole-body FDG PET/CT imaging for oncological indications on a PET/CT scanner using time-of-flight (TOF) and subsequent whole-body PET/MR imaging on an investigational hybrid PET/MRI scanner. Data sets from PET/MRI (with and without TOF) were reconstructed using MR AC and semi-quantitative segmental (20-segment model) myocardial tracer uptake (per cent of maximum) and compared to PET/CT which was reconstructed using CT AC and served as standard of reference. Excellent correlations were found for regional uptake values between PET/CT and PET/MRI with TOF (n = 460 segments in 23 patients; r = 0.913; p < 0.0001) with narrow Bland-Altman limits of agreement (-8.5 to +12.6 %). Correlation coefficients were slightly lower between PET/CT and PET/MRI without TOF (n = 460 segments in 23 patients; r = 0.851; p < 0.0001) with broader Bland-Altman limits of agreement (-12.5 to +15.0 %). PET/MRI with and without TOF showed minimal underestimation of tracer uptake (-2.08 and -1.29 %, respectively), compared to PET/CT. Relative myocardial FDG uptake obtained from MR-based attenuation corrected FDG PET is highly comparable to standard CT-based attenuation corrected FDG PET, suggesting interchangeability of both AC techniques. (orig.)

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.

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

Procedures for determining MATMOD-4V material constants

Energy Technology Data Exchange (ETDEWEB)

Lowe, T.C.

1993-11-01

The MATMOD-4V constitutive relations were developed from the original MATMOD model to extend the range of nonelastic deformation behaviors represented to include transient phenomena such as strain softening. Improvements in MATMOD-4V increased the number of independent material constants and the difficulty in determining their values. Though the constitutive relations are conceptually simple, their form and procedures for obtaining their constants can be complex. This paper reviews in detail the experiments, numerical procedures, and assumptions that have been used to determine a complete set of MATMOD-4V constants for high purity aluminum.

Probing parton dynamics of QCD matter with Ω and ϕ production

Science.gov (United States)

Adamczyk, L.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Attri, A.; Averichev, G. S.; Bai, X.; Bairathi, V.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Bouchet, J.; Brandenburg, J. D.; Brandin, A. V.; Bunzarov, I.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Campbell, J. M.; Cebra, D.; Chakaberia, I.; Chaloupka, P.; Chang, Z.; Chatterjee, A.; Chattopadhyay, S.; Chen, J. H.; Chen, X.; Cheng, J.; Cherney, M.; Christie, W.; Contin, G.; Crawford, H. J.; Das, S.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derevschikov, A. A.; di Ruzza, B.; Didenko, L.; Dilks, C.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Du, C. M.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Engelage, J.; Eppley, G.; Esha, R.; Evdokimov, O.; Eyser, O.; Fatemi, R.; Fazio, S.; Federic, P.; Fedorisin, J.; Feng, Z.; Filip, P.; Fisyak, Y.; Flores, C. E.; Fulek, L.; Gagliardi, C. A.; Garand, D.; Geurts, F.; Gibson, A.; Girard, M.; Greiner, L.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, S.; Gupta, A.; Guryn, W.; Hamad, A. I.; Hamed, A.; Haque, R.; Harris, J. W.; He, L.; Heppelmann, S.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Horvat, S.; Huang, T.; Huang, X.; Huang, B.; Huang, H. Z.; Huck, P.; Humanic, T. J.; Igo, G.; Jacobs, W. W.; Jang, H.; Jentsch, A.; Jia, J.; Jiang, K.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Khan, Z. H.; Kikoła, D. P.; Kisel, I.; Kisiel, A.; Kochenda, L.; Koetke, D. D.; Kosarzewski, L. K.; Kraishan, A. F.; Kravtsov, P.; Krueger, K.; Kumar, L.; Lamont, M. A. C.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Li, X.; Li, C.; Li, X.; Li, Y.; Li, W.; Lin, T.; Lisa, M. A.; Liu, F.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, X.; Ma, R.; Ma, G. L.; Ma, Y. G.; Ma, L.; Magdy, N.; Majka, R.; Manion, A.; Margetis, S.; Markert, C.; Matis, H. S.; McDonald, D.; McKinzie, S.; Meehan, K.; Mei, J. C.; Minaev, N. G.; Mioduszewski, S.; Mishra, D.; Mohanty, B.; Mondal, M. M.; Morozov, D. A.; Mustafa, M. K.; Nandi, B. K.; Nasim, Md.; Nayak, T. K.; Nigmatkulov, G.; Niida, T.; Nogach, L. V.; Noh, S. Y.; Novak, J.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Okorokov, V. A.; Olvitt, D.; Page, B. S.; Pak, R.; Pan, Y. X.; Pandit, Y.; Panebratsev, Y.; Pawlik, B.; Pei, H.; Perkins, C.; Pile, P.; Pluta, J.; Poniatowska, K.; Porter, J.; Posik, M.; Poskanzer, A. M.; Pruthi, N. K.; Putschke, J.; Qiu, H.; Quintero, A.; Ramachandran, S.; Raniwala, S.; Raniwala, R.; Ray, R. L.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Sakrejda, I.; Salur, S.; Sandweiss, J.; Sarkar, A.; Schambach, J.; Scharenberg, R. P.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Seger, J.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Sharma, A.; Sharma, B.; Sharma, M. K.; Shen, W. Q.; Shi, Z.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Sikora, R.; Simko, M.; Singha, S.; Skoby, M. J.; Smirnov, N.; Smirnov, D.; Solyst, W.; Song, L.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Stepanov, M.; Stock, R.; Strikhanov, M.; Stringfellow, B.; Sumbera, M.; Summa, B.; Sun, Z.; Sun, X. M.; Sun, Y.; Surrow, B.; Svirida, D. N.; Tang, Z.; Tang, A. H.; Tarnowsky, T.; Tawfik, A.; Thäder, J.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Todoroki, T.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Tripathy, S. K.; Tsai, O. D.; Ullrich, T.; Underwood, D. G.; Upsal, I.; Van Buren, G.; van Nieuwenhuizen, G.; Vandenbroucke, M.; Varma, R.; Vasiliev, A. N.; Vertesi, R.; Videbæk, F.; Vokal, S.; Voloshin, S. A.; Vossen, A.; Wang, F.; Wang, G.; Wang, J. S.; Wang, H.; Wang, Y.; Wang, Y.; Webb, G.; Webb, J. C.; Wen, L.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y.; Xiao, Z. G.; Xie, W.; Xie, G.; Xin, K.; Xu, Y. F.; Xu, Q. H.; Xu, N.; Xu, H.; Xu, Z.; Xu, J.; Yang, S.; Yang, Y.; Yang, Y.; Yang, C.; Yang, Y.; Yang, Q.; Ye, Z.; Ye, Z.; Yepes, P.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, X. P.; Zhang, Y.; Zhang, J.; Zhang, J.; Zhang, S.; Zhang, S.; Zhang, Z.; Zhang, J. B.; Zhao, F.; Zhao, J.; Zhong, C.; Zhou, L.; Zhu, X.; Zoulkarneeva, Y.; Zyzak, M.; STAR Collaboration

2016-02-01

We present measurements of Ω and ϕ production at midrapidity from Au+Au collisions at nucleon-nucleon center-of-mass energies √{sN N}=7.7 , 11.5 , 19.6 , 27, and 39 GeV by the STAR experiment at the BNL Relativistic Heavy Ion Collider (RHIC). Motivated by the coalescence formation mechanism for these strange hadrons, we study the ratios of N (Ω-+Ω¯+) /[2 N (ϕ ) ] . These ratios as a function of transverse momentum pT fall on a consistent trend at high collision energies, but start to show deviations in peripheral collisions at √{sN N}=19.6 , 27, and 39 GeV, and in central collisions at 11.5 GeV in the intermediate pT region of 2.4 -3.6 GeV/c . We further evaluate empirically the strange quark pT distributions at hadronization by studying the Ω /ϕ ratios scaled by the number of constituent quarks (NCQ). The NCQ-scaled Ω /ϕ ratios show a suppression of strange quark production in central collisions at 11.5 GeV compared to √{sN N}≥19.6 GeV. The shapes of the presumably thermal strange quark distributions in 0-60% most central collisions at 7.7 GeV show significant deviations from those in 0-10% most central collisions at higher energies. These features suggest that there is likely a change of the underlying strange quark dynamics in the transition from quark matter to hadronic matter at collision energies below 19.6 GeV.

Design guidelines for flexural wave attenuation of slender beams with local resonators

International Nuclear Information System (INIS)

Liu, Yaozong; Yu, Dianlong; Li, Li; Zhao, Honggang; Wen, Jihong; Wen, Xisen

2007-01-01

The complex band structures and attenuation spectra of flexural waves in slender beams with periodically mounted local resonators are investigated with transfer matrix method. It is noteworthy that the frequency range and attenuation coefficient of the locally resonant gap become larger in complex band structures if larger resonators were used. But given the total add-on mass of resonators, the attenuation spectra of finite beams with large but few resonators do not demonstrate such phenomena because the attenuation needs several periods to establish. So with the view of application, a large number of small local resonators widely spread along the beam are preferred given the total add-on mass to the beam

A Generalized Correction for Attenuation.

Science.gov (United States)

Petersen, Anne C.; Bock, R. Darrell

Use of the usual bivariate correction for attenuation with more than two variables presents two statistical problems. This pairwise method may produce a covariance matrix which is not at least positive semi-definite, and the bivariate procedure does not consider the possible influences of correlated errors among the variables. The method described…

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)

Development of a human live attenuated West Nile infectious DNA vaccine: Identification of a minimal mutation set conferring the attenuation level acceptable for a human vaccine

Energy Technology Data Exchange (ETDEWEB)

Yamshchikov, Vladimir, E-mail: yaximik@gmail.com; Manuvakhova, Marina; Rodriguez, Efrain; Hébert, Charles

2017-01-15

ABSTRACT: For the development of a human West Nile (WN) infectious DNA (iDNA) vaccine, we created highly attenuated chimeric virus W1806 with the serological identity of highly virulent WN-NY99. Earlier, we attempted to utilize mutations found in the E protein of the SA14-14-2 vaccine to bring safety of W1806 to the level acceptable for human use (). Here, we analyzed effects of the SA14-14-2 changes on growth properties and neurovirulence of W1806. A set including the E138K, K279M, K439R and G447D changes was identified as the perspective subset for satisfying the target safety profile without compromising immunogenicity of the vaccine candidate. The genetic stability of the attenuated phenotype was found to be unsatisfactory being dependent on a subset of attenuating changes incorporated in W1806. Elucidation of underlying mechanisms influencing selection of pathways for restoration of the envelope protein functionality will facilitate resolution of the emerged genetic stability issue. - Highlights: •Effect of mutations in E on properties of WN1806 is determined. •A subset of attenuating mutations suitable for a human vaccine is defined. •Mechanism of attenuation is proposed and illustrated. •Underlying mechanisms of neurovirulence reversion are suggested.

Subsurface Contaminant Focus Area: Monitored Natural Attenuation (MNA)--Programmatic, Technical, and Regulatory Issues

Energy Technology Data Exchange (ETDEWEB)

Krupka, Kenneth M.; Martin, Wayne J.

2001-07-23

Natural attenuation processes are commonly used for remediation of contaminated sites. A variety of natural processes occur without human intervention at all sites to varying rates and degrees of effectiveness to attenuate (decrease) the mass, toxicity, mobility, volume, or concentration of organic and inorganic contaminants in soil, groundwater, and surface water systems. The objective of this review is to identify potential technical investments to be incorporated in the Subsurface Contaminant Focus Area Strategic Plan for monitored natural attenuation. When implemented, the technical investments will help evaluate and implement monitored natural attenuation as a remediation option at DOE sites. The outcome of this review is a set of conclusions and general recommendations regarding research needs, programmatic guidance, and stakeholder issues pertaining to monitored natural attenuation for the DOE complex.

Ultrasonic attenuation in niobium II: measurements near Bsub(c2)

International Nuclear Information System (INIS)

Forgan, E.M.; Gough, C.E.

1978-01-01

The attenuation of 10 to 90 MHz longitudinal sound waves has been measured from 1.2 K upwards in the superconducting mixed state of niobium near Bsub(c2). The attenuation was determined as a function of the directly measured average induction, B, within single crystal specimens which had resistance ratios ranging from 83 to 3380. The specimens tended to the 'clean' limit (electron mean free path, 1 much greater than xi 0 , the superconducting coherence length) in which there is a strong purity dependence of the relative attenuation. For the purest crystals close to Bsub(C2), the results are in reasonable agreement with the purity and field dependence predicted by microscopic theories, and agree over a much wider field range with a phenomenological modification of these theories. Measurements of attenuation and other transport properties in clean type II superconductors by other authors are discussed and it is shown that many of the evident discrepancies can be attributed to neglect of the effects of magnetic irreversibility and crystalline anisotropy. (author)

Long Pulse Integrator of Variable Integral Time Constant

International Nuclear Information System (INIS)

Wang Yong; Ji Zhenshan; Du Xiaoying; Wu Yichun; Li Shi; Luo Jiarong

2010-01-01

A kind of new long pulse integrator was designed based on the method of variable integral time constant and deducting integral drift by drift slope. The integral time constant can be changed by choosing different integral resistors, in order to improve the signal-to-noise ratio, and avoid output saturation; the slope of integral drift of a certain period of time can be calculated by digital signal processing, which can be used to deduct the drift of original integral signal in real time to reduce the integral drift. The tests show that this kind of long pulse integrator is good at reducing integral drift, which also can eliminate the effects of changing integral time constant. According to experiments, the integral time constant can be changed by remote control and manual adjustment of integral drift is avoided, which can improve the experiment efficiency greatly and can be used for electromagnetic measurement in Tokamak experiment. (authors)

Auto type-selection of constant supporting in nuclear power stations

International Nuclear Information System (INIS)

Liu Hu; Wang Fujun; Liu Wei; Li Zhaoqing

2013-01-01

To solve the type-selection of constant supporting in nuclear power stations, combining the characteristics of constant supporting which can adjust in the certain scope and the rules of load-displacement, the requirements and process for the type-selection of constant supporting is proposed, and the process of type-selection is optimized by Visual Basic. After inputting of the known parameters, the process can automatically select the most economical and reasonable constant supporting by array and function. (authors)

The frequency attenuation effect in identity and associative priming.

Science.gov (United States)

Nievas, Francisco

2010-05-01

Three lexical decision experiments were carried out, where the masked priming paradigm is used to study the role of the frequency attenuation effect (more priming in low-frequency target words than in high-frequency target words) in repetition and associative priming, manipulating Prime Duration (PD) and Stimulus Onset Asynchrony (SOA). A new concept was introduced, Minimum Time Threshold (MTT), this is, the minimum time interval of exposure to the masked word in order to become aware of it. Results support the notion that MTT is a key to the appearance of the frequency attenuation effect when enough word processing time is allowed. Results do not support the unified explanation of masked priming and long-term priming as proposed by Bodner and Masson (2001). Moreover, information feedback from the semantic level was not the reason for the frequency attenuation effect in repetition priming.

Variación temporal de las constantes fundamentales

Science.gov (United States)

Landau, S. J.; Vucetich, H.

La variación temporal de las constantes fundamentales es un problema que ha motivado numerosos trabajos teóricos y experimentales desde la hipótesis de los grandes números de Dirac en 1937. Entre los métodos experimentales y observacionales para establecer restricciones sobre la variación de las constantes fundamentes es importante mencionar: comparación entre relojes atómicos[1], métodos geofísicos[2][3], análisis de sistemas de absorción en quasares[4][5][6] y cotas provenientes de la nucleosíntesis primordial[7]. En un trabajo reciente[5], se reportó una significativa variación en la constante de estructura fina. Intentos de unificar las cuatro interacciones fundamentales dieron como resultado teorías con múltiples dimensiones como las teorías de Kaluza-Klein y teorías de supercuerdas. Estas teorías proporcionan un marco teórico natural para el estudio de la variación temporal de las constantes fundamentales. A su vez, un modelo sencillo para estudiar la variación de la constante de estructura fina, fue propuesto en [8], a partir de premisas muy generales como ser covarianza, invarianza de gauge, causalidad y invarianza ante reversiones temporales en el electromagnetismo. Diferentes versiones de las teorías antes mencionadas coinciden en predecir variaciones temporales de las constantes fundamentales pero difieren en la forma de esta variación[9][10]. De esta manera, las restricciones establecidas experimentalmente sobre la variación de las constantes fundamentales pueden ser una herramienta importante para testear estas diferentes teorías. En este trabajo, utilizamos las cotas provenientes de diversas técnicas experimentales, para testear si las mismas son consistentes con alguna de las teorías antes mencionadas. En particular, establecemos cotas sobre la variación de los parámentros libres de las diferentes teorías como por ejemplo el radio de las dimensiones extras en las teorías tipo Kaluza-Klein.

Fast optimization algorithms and the cosmological constant

Science.gov (United States)

Bao, Ning; Bousso, Raphael; Jordan, Stephen; Lackey, Brad

2017-11-01

Denef and Douglas have observed that in certain landscape models the problem of finding small values of the cosmological constant is a large instance of a problem that is hard for the complexity class NP (Nondeterministic Polynomial-time). The number of elementary operations (quantum gates) needed to solve this problem by brute force search exceeds the estimated computational capacity of the observable Universe. Here we describe a way out of this puzzling circumstance: despite being NP-hard, the problem of finding a small cosmological constant can be attacked by more sophisticated algorithms whose performance vastly exceeds brute force search. In fact, in some parameter regimes the average-case complexity is polynomial. We demonstrate this by explicitly finding a cosmological constant of order 10-120 in a randomly generated 1 09-dimensional Arkani-Hamed-Dimopoulos-Kachru landscape.

Convexity and concavity constants in Lorentz and Marcinkiewicz spaces

Science.gov (United States)

Kaminska, Anna; Parrish, Anca M.

2008-07-01

We provide here the formulas for the q-convexity and q-concavity constants for function and sequence Lorentz spaces associated to either decreasing or increasing weights. It yields also the formula for the q-convexity constants in function and sequence Marcinkiewicz spaces. In this paper we extent and enhance the results from [G.J.O. Jameson, The q-concavity constants of Lorentz sequence spaces and related inequalities, Math. Z. 227 (1998) 129-142] and [A. Kaminska, A.M. Parrish, The q-concavity and q-convexity constants in Lorentz spaces, in: Banach Spaces and Their Applications in Analysis, Conference in Honor of Nigel Kalton, May 2006, Walter de Gruyter, Berlin, 2007, pp. 357-373].

High-intensity sprint fatigue does not alter constant-submaximal velocity running mechanics and spring-mass behavior.

Science.gov (United States)

Morin, Jean-Benoit; Tomazin, Katja; Samozino, Pierre; Edouard, Pascal; Millet, Guillaume Y

2012-04-01

We investigated the changes in constant velocity spring-mass behavior after high intensity sprint fatigue in order to better interpret the results recently reported after ultra-long distance (ULD) exercises. Our hypothesis was that after repeated sprints (RS), subjects may likely experience losses of force such as after ULD, but the necessity to modify their running pattern to attenuate the overall impact at each step (such as after ULD) may not be present. Eleven male subjects performed four sets of five 6-s sprints with 24-s recovery between sprints and 3 min between sets, on a sprint treadmill and on a bicycle ergometer. For each session, their running mechanics and spring-mass characteristics were measured at 10 and 20 km h(-1) on an instrumented treadmill before and after RS. Two-way (period and velocity) ANOVAs showed that high-intensity fatigue did not induce any change in the constant velocity running pattern at low or high velocity, after both running and cycling RS, despite significant decreases (P < 0.001) in maximal power (-27.1 ± 8.2% after running RS and -15.4 ± 11.5 % after cycling RS) and knee extensors maximal voluntary force (-18.8 ± 6.7 % after running RS and -15.0 ± 7.6 % after cycling RS). These results bring indirect support to the hypothesis put forward in recent ULD studies that the changes in running mechanics observed after ULD are likely not related to the decrease in strength capabilities, but rather to the necessity for subjects to adopt a protective running pattern.

Parametrised Constants and Replication for Spatial Mobility

DEFF Research Database (Denmark)

Hüttel, Hans; Haagensen, Bjørn

2009-01-01

Parametrised replication and replication are common ways of expressing infinite computation in process calculi. While parametrised constants can be encoded using replication in the π-calculus, this changes in the presence of spatial mobility as found in e.g. the distributed π- calculus...... of the distributed π-calculus with parametrised constants and replication are incomparable. On the other hand, we shall see that there exists a simple encoding of recursion in mobile ambients....

Attenuation of gamma radiation in concrete shields

International Nuclear Information System (INIS)

Azevedo e Souza, A.C. de.

1978-12-01

The attenuation characteristics of γ radiation in concrete layers considering their mechanical resistence and densities were determined. A 137 Cs source was used in a 'good geometry' arrangement to eliminate the effects of the buildup factor. The ordinary and the heavy concrete were irradiated and for the latter it was used as additives iron ore and Fe 2 O 3 pellets in various grain sizes. The detection system consisted of a 2' x 2' NaI (Tl) crystal coupled to a photomultiplier tube and the associated electronic equipment. FORTRAN programs were used for determining the absorption coefficients and the attenuation factors. These programs calculate photopeak areas eliminating all contributions due to Compton effect and background. (Author) [pt

Indoor signal attenuation assessment via fuzzy logic

Directory of Open Access Journals (Sweden)

Alexandre de Assis Mota

2011-09-01

Full Text Available This work focuses on the analysis of signal´s attenuation in indoor environments using a fuzzy logic approach based on the Shadowing Signal Propagation Model (SSPM. The SSPM allows the characterization of the attenuation caused by the environment through the ? parameter present in this model. In addition to this, the Fuzzy Logic provides a form of approximate reasoning that allows the treatment of problems with incomplete, vague and imprecise information. Also, it offers a simple way to obtain a possible solution for a problem using the heuristic knowledge about a particular situation. The results show that the methodology produced satisfactory results, close to the ones yielded by experimental methods.

Sirtuin 7 promotes cellular survival following genomic stress by attenuation of DNA damage, SAPK activation and p53 response

Energy Technology Data Exchange (ETDEWEB)

Kiran, Shashi; Oddi, Vineesha [Laboratory of Cancer Biology, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, Telangana, 500001 (India); Ramakrishna, Gayatri, E-mail: gayatrirama1@gmail.com [Laboratory of Cancer Biology, Centre for DNA Fingerprinting and Diagnostics, Hyderabad, Telangana, 500001 (India); Laboratory of Cancer Cell Biology, Department of Research, Institute of Liver and Biliary Sciences, Delhi 110070 (India)

2015-02-01

Maintaining the genomic integrity is a constant challenge in proliferating cells. Amongst various proteins involved in this process, Sirtuins play a key role in DNA damage repair mechanisms in yeast as well as mammals. In the present work we report the role of one of the least explored Sirtuin viz., SIRT7, under conditions of genomic stress when treated with doxorubicin. Knockdown of SIRT7 sensitized osteosarcoma (U2OS) cells to DNA damage induced cell death by doxorubicin. SIRT7 overexpression in NIH3T3 delayed cell cycle progression by causing delay in G1 to S transition. SIRT7 overexpressing cells when treated with low dose of doxorubicin (0.25 µM) showed delayed onset of senescence, lesser accumulation of DNA damage marker γH2AX and lowered levels of growth arrest markers viz., p53 and p21 when compared to doxorubicin treated control GFP expressing cells. Resistance to DNA damage following SIRT7 overexpression was also evident by EdU incorporation studies where cellular growth arrest was significantly delayed. When treated with higher dose of doxorubicin (>1 µM), SIRT7 conferred resistance to apoptosis by attenuating stress activated kinases (SAPK viz., p38 and JNK) and p53 response thereby shifting the cellular fate towards senescence. Interestingly, relocalization of SIRT7 from nucleolus to nucleoplasm together with its co-localization with SAPK was an important feature associated with DNA damage. SIRT7 mediated resistance to doxorubicin induced apoptosis and senescence was lost when p53 level was restored by nutlin treatment. Overall, we propose SIRT7 attenuates DNA damage, SAPK activation and p53 response thereby promoting cellular survival under conditions of genomic stress. - Highlights: • Knockdown of SIRT7 sensitized cells to DNA damage induced apoptosis. • SIRT7 delayed onset of premature senescence by attenuating DNA damage response. • Overexpression of SIRT7 delayed cell cycle progression by delaying G1/S transition. • Upon DNA damage SIRT

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

International Nuclear Information System (INIS)

Ye Peng-Cheng; Pan Guang

2015-01-01

Due to the high speed of underwater vehicles, cavitation is generated inevitably along with the sound attenuation when the sound signal traverses through the cavity region around the underwater vehicle. The linear wave propagation is studied to obtain the influence of bubbly liquid on the acoustic wave propagation in the cavity region. The sound attenuation coefficient and the sound speed formula of the bubbly liquid are presented. Based on the sound attenuation coefficients with various vapor volume fractions, the attenuation of sound intensity is calculated under large cavitation number conditions. The result shows that the sound intensity attenuation is fairly small in a certain condition. Consequently, the intensity attenuation can be neglected in engineering. (paper)

Detailed study of seismic wave attenuation from four oilfields in Abu Dhabi, United Arab Emirates

Science.gov (United States)

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

2018-02-01

In the present study, we provide a detailed study of seismic wave attenuation obtained from four oilfields. The reservoir zones of these oilfields are complicated due to complex fracture networks, the presence of tar mat and high heterogeneity of carbonate rocks of which the subsurface of Abu Dhabi is mainly composed. These complexities decrease signal-to-noise ratio and make attenuation estimation difficult. We obtained high-resolution attenuation profiles from vertical seismic profiling (VSP) and sonic waveform data. The VSP data were recorded in all four oilfields and the sonic data were acquired in the reservoir zones of oilfields I and IV. We found that the VSP scattering attenuation ({Q}{{S}{{c}}{{a}}{{t}}}-1) varies from -0.080 to 0.180 over a depth range of 400-3500 m. We attributed this significant scattering to the high heterogeneity of carbonate rocks. The scattering profiles seem to be sensitive to fractures, lithology heterogeneity and tar mat, but their effect is superimposed. The VSP intrinsic attenuation varies from -0.15 to 0.246 with high variation within each formation. Since intrinsic attenuation is closely related to fluids, we assumed that this variation is due to the non-uniform distribution of fluids caused by the complex porosity network of the subsurface. The sonic monopole attenuation ({Q}{{M}{{f}}}-1) in the reservoir zones ranges between 0.033-0.094 and dipole inline attenuation ({Q}{{I}{{n}}{{l}}}-1) ranges from 0.040-0.138. The sonic attenuation appears to be sensitive to the presence of fluid and type of fractures, where it shows high attenuation for open fractures and low attenuation for resistive fractures. The zones with high clay content display high sonic intrinsic attenuation in the reservoir of oilfield II. We explain this by the frictional movement between the clay and carbonates due to the elasticity contrast of these two materials. Therefore, the solid grain friction may be the dominant attenuation mechanism in those zones.

Mid-European seismic attenuation anomaly

Czech Academy of Sciences Publication Activity Database

Málek, Jiří; Brokešová, J.; Vackář, Jiří

2017-01-01

Roč. 712, AUG 21 (2017), s. 557-577 ISSN 0040-1951 Grant - others:AV ČR(CZ) StrategieAV21/4 Program:StrategieAV Institutional support: RVO:67985891 Keywords : seismic wave attenuation * peak ground motion * H/V ratio Subject RIV: DC - Siesmology, Volcanology, Earth Structure OBOR OECD: Geology Impact factor: 2.693, year: 2016

On the cosmical constant

International Nuclear Information System (INIS)

Chandra, R.

1977-01-01

On the grounds of the two correspondence limits, the Newtonian limit and the special theory limit of Einstein field equations, a modification of the cosmical constant has been proposed which gives realistic results in the case of a homogeneous universe. Also, according to this modification an explanation for the negative pressure in the steady-state model of the universe has been given. (author)

Coupling constants deduced for the resonances in kaon photo-production

International Nuclear Information System (INIS)

Cheoun, M. K.; Kim, K. S.; Choi, T. K.

2004-01-01

We deduced the coupling constants of nucleon and hyperon resonances, which participate in kaon productions as intermediate states that are formed by electro-magnetic probes and that finally decay into hadronic final states. We used an isobaric model based on an effective Lagrangian approach to describe the processes, in which relevant coupling constants regarding related resonances are effectively determined by fitting available experimental data. Our scheme to deduce the coupling constants was as follows: First, we calculated the lower and the upper limits on the coupling constants by using the experimental decay data available until now and/or theoretical predictions, such as those from quark models and SU(3) symmetry. Second, we exploited those limits as physical constraints on our fitting scheme for the kaon photo-production data. Finally, the deduced values and regions of the coupling constants, which satisfy not only the reaction data but also the decay data, are presented as figures with respect to the strong and the electro-magnetic coupling constants, and their multiplicative values. Our results for the coupling constants give physical values that are more restricted than those allowed by the experimental data nowadays.

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

Shifting from constant-voltage to constant-current in Parkinson's disease patients with chronic stimulation.

Science.gov (United States)

Amami, P; Mascia, M M; Franzini, A; Saba, F; Albanese, A

2017-08-01

The study aimed to evaluate safety and efficacy of shifting stimulation settings from constant-voltage (CV) to constant-current (CC) programming in patients with Parkinson's disease (PD) and chronic subthalamic nucleus deep brain stimulation (STN DBS). Twenty PD patients with chronic STN DBS set in CV programming were shifted to CC and followed for 3 months; the other stimulation settings and the medication regimen remained unchanged. Side effects, motor, non-motor, executive functions, and impedance were assessed at baseline and during follow-up. No adverse events were observed at time of shifting or during CC stimulation. Motor and non-motor measures remained unchanged at follow-up despite impedance decreased. Compared to baseline, inhibition processes improved at follow-up. The shifting strategy was well tolerated and the clinical outcome was maintained with no need to adjust stimulation settings or medications notwithstanding a decrease of impedance. Improvement of inhibition processes is a finding which needed further investigation.

Problems of experimental determination of mononuclear hydroxocomplexes stability constants

International Nuclear Information System (INIS)

Davydov, Yu. P.; Davydov, D. Yu.

2003-01-01

In order to determine the stability constants of hydroxocomplexes a methodical approach has been developed that involves the following steps: (1) Determination of pH and concentration intervals in which a metal is present only in a form of mononuclear hydroxocomplex in solution; (2) determination of initial form of hydrated cation and conditions under which it occurs in solution; (3) Determination of the forms of mononuclear hydroxocomplexes and their stability constants by at least two independent methods. This paper illustrates application of the above approach for Fe(III) hydroxocomplex stability constant determination. The hydrolysis with formation of mononuclear species was studied at lower iron concentration since a pH interval is wider in that case (pH 3+ (H 2 O) 6 in the interval of pH 1.0 - 1.5. Further increase of pH (higher than 1.5) leads to hydrolysis of Fe with formation of mononuclear hydroxocomplexes. The results of ion exchange and spectrophotometry experiments showed that in a pH interval 1.5- 3.0 Fe(III) form only one complex Fe(OH)2+. The stability constant of iron first hydroxocomplex has been calculated. Applying the above approach for studying a series of cation we came to a conclusion that nearly in every case only the first hydroxocomplex stability stability constant can be experimentally determined. Only in the case of Pu(IV) it was possible to determine also the second constant. This paper demonstrates also application of the above approach for calculation of the Pu(IV) hydroxocomplexes stability constants. (authors)

Contaminant Attenuation and Transport Characterization of 200-UP-1 Operable Unit Sediment Samples

Energy Technology Data Exchange (ETDEWEB)

Lee, Brady D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Szecsody, James E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Qafoku, Nikolla [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); McElroy, Erin M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Baum, Steven R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Snyder, Michelle MV [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lawter, Amanda R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Resch, Charles T. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Gartman, Brandy N. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zhong, Lirong [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Saunders, Danielle L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Williams, Benjamin D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Horner, Jacob A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Leavy, Ian I. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Christiansen, Beren B. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Clayton, Ray E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Johnson, Kayla C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2017-09-27

Contaminants disposed of at the land surface migrate through the vadose zone, forming plumes in groundwater. Processes that occur in the groundwater can attenuate contaminant concentrations during transport through the aquifer. For this reason, quantifying contaminant attenuation and contaminant transport processes in the aquifer, in support of the conceptual site model (CSM) and fate and transport modeling, are important for assessing the need for, and type of, remediation in the groundwater, including monitored natural attenuation (MNA). The framework to characterize attenuation and transport processes provided in U.S. Environmental Protection Agency (EPA) guidance documents was used to guide the laboratory effort reported herein.

Nuclear magnetic resonance J coupling constant polarizabilities of hydrogen peroxide

DEFF Research Database (Denmark)

Kjær, Hanna; Nielsen, Monia R.; Pagola, Gabriel I.

2012-01-01

In this paper we present the so far most extended investigation of the calculation of the coupling constant polarizability of a molecule. The components of the coupling constant polarizability are derivatives of the NMR indirect nuclear spin-spin coupling constant with respect to an external elec...

Intercomparison of medium-energy neutron attenuation in iron and concrete

International Nuclear Information System (INIS)

Hirayama, H.

1999-01-01

Neutron attenuation of medium energy below 1 GeV has not been well understood until now. It is desired to obtain common agreements concerning the behaviours of neutrons inside various materials. This is necessary in order to agree on definitions of the attenuation length, which is very important for shielding calculations involving high energy accelerators. As one attempt, it was proposed by Japanese attendants of SATIF-2 to compare the attenuation of medium-energy neutrons inside iron and concrete shields between various computer codes and data, and was cited as a suitable action for SATIF. The first results from three groups were presented at SATIF-3. It has become clear that neutrons above 20 MeV are important for understanding the attenuation inside materials and that the geometry, planar or spherical, does not affect the results very much. Considering the CPU times required for Monte Carlo calculations and this result, revised problems to be calculated were prepared by the Japanese Working Group and sent to the participants of this action. The geometry is only plane, and calculations are required only for neutrons above 20 MeV. The secondary neutrons from high energy protons, which were calculated by H. Nakashima, are also included in the problem. The results from four groups were sent to the organizer at the end of August. This paper presents a comparison between groups concerning the attenuation length together with the neutron spectrum and the future themes which come from this intercomparison. (author)

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.

The geometry of plane waves in spaces of constant curvature

International Nuclear Information System (INIS)

Tran, H.V.

1988-01-01

We examined the geometry of possible plane wave fronts in spaces of constant curvature for three cases in which the cosmological constant is positive, zero, or negative. The cosmological constant and a second-order invariant determined by a congruence of null rays were used in the investigation. We embedded the spaces under investigation in a flat five-dimensional space, and studied the null hyperplanes passing through the origin of the flat five-dimensional space. The embedded spaces are represented by quadrics in the five-dimensional space. The plane wave fronts are represented by the intersection of the quadric with null hyperplanes passing through the origin of the five-dimensional space. We concluded that in Minkowski spaces (zero cosmological constant), the plane-fronted waves will intersect if and only if the second-order invariant mentioned above is non-zero. For deSitter spaces (positive cosmological constant), plane-fronted waves will always intersect. For anti-deSitter spaces (negative cosmological constant), plane-fronted waves may but need not intersect

The cosmological constant, branes and non-geometry

International Nuclear Information System (INIS)

Gautason, Fridhrik Freyr

2014-01-01

In this thesis we derive an equation for the classical cosmological constant in general string compactifications by employing scaling symmetries present in string theory. We find that in heterotic string theory, a perturbatively small, but non-vanishing, cosmological constant is impossible unless non-perturbative and/or string loop corrections are taken into account. In type II string theory we show that the classical cosmological constant is given by a sum of two terms, the source actions evaluated on-shell, and a certain combination of non-vanishing fluxes integrated over spacetime. In many cases we can express the classical cosmological constant in terms of only the source contributions by exploiting two scaling symmetries. This result can be used in two ways. First one can simply predict the classical cosmological constant in a given setup without solving all equations of motion. A second application is to give constraints on the near brane behavior of supergravity fields when the cosmological constant is known. In particular we motivate that energy densities of some fields diverge in the well-known KKLT scenario for de Sitter solutions in type IIB string theory. More precisely, we show, using our results and minimal assumptions, that energy densities of the three-form fluxes diverge in the near-source region of internal space. This divergence is unusual, since these fields do not directly couple to the source, and has been interpreted as a hint of instability of the solution. In the last chapter of the thesis we discuss the worldvolume actions of exotic five-branes. Using a specific chain of T- and S-dualities in a spacetime with two circular isometries, we derive the DBI and WZ actions of the so-called 5 2 2 - and 5 2 3 -brane. These actions describe the dynamics of the branes as well as their couplings to the ten-dimensional gauge potentials. We propose a modified Bianchi identity for the non-geometric Q-flux due to one of the branes. Q-flux often appears

Constant Cremer, voetballer in Tilburg met Afrikaanse wortels

NARCIS (Netherlands)

Drs. Thijs Kemmeren

2012-01-01

Constant Cremer is de eerste zwarte voetballer in Nederland. Hij is geboren in Belgisch Congo. Hij speelde bij Willem II in het seizoen 1904 -1905 en werd met Willem II Brabvants kampioen. Constant werd, als een donkere mulat een held in Tilburg. Hij kwam uiteindelijk terecht in Nederland Indie en

Monitored Natural Attenuation of ino9rganic Contaminants Treatability Study Final Report

Energy Technology Data Exchange (ETDEWEB)

Crapse, K

2004-05-19

The identification and quantification of key natural attenuation processes for inorganic contaminants at D-Area is detailed herein. Two overarching goals of this evaluation of monitored natural attenuation (MNA) as a remediation strategy were (1) to better define the availability of inorganic contaminants as potential sources for transport to groundwater and uptake by environmental receptors and (2) to understand the site-specific mechanisms controlling attenuation of these inorganic contaminants through tandem geochemical and biological characterization. Data collected in this study provides input for more appropriate site groundwater transport models. Significant natural attenuation is occurring at D-Area as evidenced by relatively low aqueous concentrations of constituents of concern (COCs) (Be, Ni, U, and As) at all locations characterized and the decrease in groundwater concentrations with increasing distance from the source. The observed magnitude of decrease in groundwater concentrations of COCs with distance from the D-Area Coal Pile Runoff Basin (DCPRB) could not be accounted for by the modeled physical attenuation processes of dilution/dispersion. This additional attenuation, i.e., the observed difference between the groundwater concentrations of COCs and the modeled physical attenuation, is due to biogeochemical processes occurring at the D-Area. In tandem geochemical and microbiological characterization studies designed to evaluate the mechanisms contributing to natural attenuation, pH was the single parameter found to be most predictive of contaminant attenuation. The increasing pH with distance from the source is likely responsible for increased sorption of COCs to soil surfaces within the aquifer at D-Area. Importantly, because the sediments appear to have a high buffering capacity, the acid emanating from the DCPRB has been neutralized by the soil, and these conditions have led to large Kd values at the site. Two major types of soils are present at

Can Survival Bias Explain the Age Attenuation of Racial Inequalities in Stroke Incidence?: A Simulation Study.

Science.gov (United States)

Mayeda, Elizabeth Rose; Banack, Hailey R; Bibbins-Domingo, Kirsten; Zeki Al Hazzouri, Adina; Marden, Jessica R; Whitmer, Rachel A; Glymour, M Maria

2018-07-01

In middle age, stroke incidence is higher among black than white Americans. For unknown reasons, this inequality decreases and reverses with age. We conducted simulations to evaluate whether selective survival could account for observed age patterning of black-white stroke inequalities. We simulated birth cohorts of 20,000 blacks and 20,000 whites with survival distributions based on US life tables for the 1919-1921 birth cohort. We generated stroke incidence rates for ages 45-94 years using Reasons for Geographic and Racial Disparities in Stroke (REGARDS) study rates for whites and setting the effect of black race on stroke to incidence rate difference (IRD) = 20/10,000 person-years at all ages, the inequality observed at younger ages in REGARDS. We compared observed age-specific stroke incidence across scenarios, varying effects of U, representing unobserved factors influencing mortality and stroke risk. Despite a constant adverse effect of black race on stroke risk, the observed black-white inequality in stroke incidence attenuated at older age. When the hazard ratio for U on stroke was 1.5 for both blacks and whites, but U only directly influenced mortality for blacks (hazard ratio for U on mortality =1.5 for blacks; 1.0 for whites), stroke incidence rates in late life were lower among blacks (average observed IRD = -43/10,000 person-years at ages 85-94 years versus causal IRD = 20/10,000 person-years) and mirrored patterns observed in REGARDS. A relatively moderate unmeasured common cause of stroke and survival could fully account for observed age attenuation of racial inequalities in stroke.

The Cosmological Constant Problem (1/2)

CERN Multimedia

CERN. Geneva

2015-01-01

I will review the cosmological constant problem as a serious challenge to our notion of naturalness in Physics. Weinberg’s no go theorem is worked through in detail. I review a number of proposals possibly including Linde's universe multiplication, Coleman's wormholes, the fat graviton, and SLED, to name a few. Large distance modifications of gravity are also discussed, with causality considerations pointing towards a global modification as being the most sensible option. The global nature of the cosmological constant problem is also emphasized, and as a result, the sequestering scenario is reviewed in some detail, demonstrating the cancellation of the Standard Model vacuum energy through a global modification of General Relativity.

The Cosmological Constant Problem (2/2)

CERN Multimedia

CERN. Geneva

2015-01-01

I will review the cosmological constant problem as a serious challenge to our notion of naturalness in Physics. Weinberg’s no go theorem is worked through in detail. I review a number of proposals possibly including Linde's universe multiplication, Coleman's wormholes, the fat graviton, and SLED, to name a few. Large distance modifications of gravity are also discussed, with causality considerations pointing towards a global modification as being the most sensible option. The global nature of the cosmological constant problem is also emphasized, and as a result, the sequestering scenario is reviewed in some detail, demonstrating the cancellation of the Standard Model vacuum energy through a global modification of General Relativity.

Improvements to the Chebyshev expansion of attenuation correction factors for cylindrical samples

International Nuclear Information System (INIS)

Mildner, D.F.R.; Carpenter, J.M.

1990-01-01

The accuracy of the Chebyshev expansion coefficients used for the calculation of attenuation correction factors for cylinderical samples has been improved. An increased order of expansion allows the method to be useful over a greater range of attenuation. It is shown that many of these coefficients are exactly zero, others are rational numbers, and others are rational frations of π -1 . The assumptions of Sears in his asymptotic expression of the attenuation correction factor are also examined. (orig.)

Critical experiments analysis by ABBN-90 constant system

Energy Technology Data Exchange (ETDEWEB)

Tsiboulia, A.; Nikolaev, M.N.; Golubev, V. [Institute of Physics and Power Engineering, Obninsk (Russian Federation)] [and others

1997-06-01

The ABBN-90 is a new version of the well-known Russian group-constant system ABBN. Included constants were calculated based on files of evaluated nuclear data from the BROND-2, ENDF/B-VI, and JENDL-3 libraries. The ABBN-90 is intended for the calculation of different types of nuclear reactors and radiation shielding. Calculations of criticality safety and reactivity accidents are also provided by using this constant set. Validation of the ABBN-90 set was made by using a computerized bank of evaluated critical experiments. This bank includes the results of experiments conducted in Russia and abroad of compact spherical assemblies with different reflectors, fast critical assemblies, and fuel/water-solution criticalities. This report presents the results of the calculational analysis of the whole collection of critical experiments. All calculations were produced with the ABBN-90 group-constant system. Revealed discrepancies between experimental and calculational results and their possible reasons are discussed. The codes and archives INDECS system is also described. This system includes three computerized banks: LEMEX, which consists of evaluated experiments and their calculational results; LSENS, which consists of sensitivity coefficients; and LUND, which consists of group-constant covariance matrices. The INDECS system permits us to estimate the accuracy of neutronics calculations. A discussion of the reliability of such estimations is finally presented. 16 figs.

Mapping of the mutations present in the genome of the Rift Valley fever virus attenuated MP12 strain and their putative role in attenuation.

Science.gov (United States)

Vialat, P; Muller, R; Vu, T H; Prehaud, C; Bouloy, M

1997-11-01

The MP12 attenuated strain of Rift Valley fever virus was obtained by 12 serial passages of a virulent isolate ZH548 in the presence of 5-fluorouracil (Caplen et al., 1985. Mutagen-directed attenuation of Rift Valley fever virus as a method for vaccine development. J. Gen. Virol., 66, 2271-2277). The comparison of the M segment of the two strains has already been reported by Takehara et al. (Takehara et al., 1989. Identification of mutations in the M RNA of a candidate vaccine strain of Rift Valley fever virus. Virology 169, 452-457). We have completed the comparison and found that altogether a total of nine, 12 and four nucleotides were changed in the L, M and S segments of the two strains, respectively. Three mutations induced amino acid changes in the L protein but none of them was located in the recognized motifs conserved among RNA dependent polymerases. In the S segment, a single change modified an amino acid in the NSs protein and in the M segment, seven of the mutations resulted in amino acid changes in each of the four encoded G1, G2, 14 kDa and 78 kDa proteins. Characterization of the MP12 virus indicated that determinants for attenuation were present in each segment and that they were introduced progressively during the 12 passages in the presence of the mutagen (Saluzzo and Smith, 1990. Use of reassortant viruses to map attenuating and temperature-sensitive mutations of the Rift Valley fever virus MP-12 vaccine. Vaccine 8, 369-375). Passages 4 and 7-9 were found to be essential for introduction of temperature-sensitive lesions and attenuation. In an attempt to correlate some of the mutations with the attenuated or temperature-sensitive phenotypes, we determined by sequencing the passage level at which the different mutations appeared. This work should help to address the question of the role of the viral gene products in Rift Valley fever pathogenesis.

The determination methods of the velocity constant for electrochemical reactions; Les methodes de determination de la constante de vitesse des reactions electrochimiques

Energy Technology Data Exchange (ETDEWEB)

Molina, R

1963-07-01

In a brief introduction are recalled the fundamental mechanisms of the electrochemical reaction and the definition of the intrinsic velocity constant of a such reaction. By the nature of the different parameters which enter in this definition are due some experimental problems which are examined. Then are given the principles of the measurement methods of the velocity constant. These methods are developed with the mathematical expression of the different rates of the mass transfer to an electrode. In each case are given the experimental limits of use of the methods and the size order of the velocity constant that can be reached. A list of fundamental works to be consulted conclude this work. (O.M.) [French] Dans une breve introduction sont rappeles les mecanismes fondamentaux de la reaction electrochimique et la definition de la constante de vitesse intrinseque d'une telle reaction. De la nature des differents parametres qui entrent dans celle definition, decoulent un certain nombre de problemes experimentaux qui sont passes en revue. On donne ensuite les principes des methodes de mesure de la constante de vitesse. L'exposition de ces methodes est developpee a l'aide de l'expression mathematique des differents regimes de transfert de masse a une electrode. On s'attache dans chaque cas, a donner les limitations experimentales d'utilisation des methodes et l'ordre de grandeur de la constante de vitesse qu'elles permettent d'atteindre. Une liste des ouvrages fondamentaux a consulter conclut ce travail. (auteur)

A model for solar constant secular changes

Science.gov (United States)

Schatten, Kenneth H.

1988-01-01

In this paper, contrast models for solar active region and global photospheric features are used to reproduce the observed Active Cavity Radiometer and Earth Radiation Budget secular trends in reasonably good fashion. A prediction for the next decade of solar constant variations is made using the model. Secular trends in the solar constant obtained from the present model support the view that the Maunder Minimum may be related to the Little Ice Age of the 17th century.

Renormalization group equations with multiple coupling constants

International Nuclear Information System (INIS)

Ghika, G.; Visinescu, M.

1975-01-01

The main purpose of this paper is to study the renormalization group equations of a renormalizable field theory with multiple coupling constants. A method for the investigation of the asymptotic stability is presented. This method is applied to a gauge theory with Yukawa and self-quartic couplings of scalar mesons in order to find the domains of asymptotic freedom. An asymptotic expansion for the solutions which tend to the origin of the coupling constants is given

High temperature elastic constant measurements: application to plutonium; Mesure des constantes elastiques a haute temperature application au plutonium

Energy Technology Data Exchange (ETDEWEB)

Bouchet, J M [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1969-03-01

We present an apparatus with which we have measured the Young's modulus and the Poisson's ratio of several compounds from the resonance frequency of cylinders in the temperature range 0 deg. C-700 deg. C. We especially studied the elastic constants of plutonium and measured for the first time to our knowledge the Young's modulus of Pu{sub {delta}} and Pu{sub {epsilon}}. E{sub {delta}} 360 deg. C = 1.6 10{sup 11} dy/cm{sup 2}; E{sub {epsilon}} 490 deg. C = 1.1 10{sup 11} dy/cm{sup 2}, {sigma}{sub {epsilon}} = 0.25 {+-} 0.03 Using our results, we have calculated the compressibility, the Debye temperature, the Grueneisen constant and the electronic specific heat of Pu{sub {epsilon}}. (author) [French] Nous decrivons un appareil qui permet de mesurer les constantes elastiques (module de Young et module de Poisson) jusqu'a 700 deg. C a partir des frequences de resonance de barreaux cylindriques. Nous avons plus specialement etudie le plutonium et determine pour la premiere fois a notre connaissance le module de Young des phases {delta} et {epsilon}: E{sub {delta}} 360 deg. C = 1.6 10{sup 11} dy/cm{sup 2}; E{sub {epsilon}} 490 deg. C = 1.1 10{sup 11} dy/cm{sup 2}, {sigma}{sub {epsilon}} = 0.25 {+-} 0.03 Nos mesures nous ont permis de calculer la compressibilite, la temperature de Debye, la constante de Gruneisen et la chaleur specifique electronique de Pu{sub {epsilon}}. (auteur)

Evaluation of dose attenuation factor of armored car against radiation accidents

International Nuclear Information System (INIS)

Sato, Tatsuhiko; Fujii, Katsutoshi; Murayama, Takashi

2002-03-01

The Tokyo Fire Department developed an armored car against radiation accidents. The car is covered by lead shields for attenuating dose from gamma rays. Dose from neutrons also can be attenuated by pouring water into tanks attached to the surface of the car. However, dose attenuation factors of the radiation shields had been determined by an estimation of single-layer shield, and more precise evaluation of multi-layer shield was required. By request from the Tokyo Fire Department, a precise evaluation of the dose attenuation in multi-layer shield was carried out. The evaluation was made by a Monte Carlo radiation transport simulation code MCNP4B for the shields used in the front, side and back of the car. Three types of the radiation sources ( 252 Cf as a neutron source, 60 Co as a gamma ray source, and radiation source corresponding to the JCO criticality accident) were considered in the calculation. Benchmark experiments using neutron and gamma ray sources were also performed for ensuring the evaluation method. As a result, it was found out that doses of neutron and gamma ray were attenuated to approximately 10% and 25% by the thickest shield, respectively. These values were close to the ones which had already obtained by the estimation of single-layer shield. (author)

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.

The contrasting roles of Planck's constant in classical and quantum theories

Science.gov (United States)

Boyer, Timothy H.

2018-04-01

We trace the historical appearance of Planck's constant in physics, and we note that initially the constant did not appear in connection with quanta. Furthermore, we emphasize that Planck's constant can appear in both classical and quantum theories. In both theories, Planck's constant sets the scale of atomic phenomena. However, the roles played in the foundations of the theories are sharply different. In quantum theory, Planck's constant is crucial to the structure of the theory. On the other hand, in classical electrodynamics, Planck's constant is optional, since it appears only as the scale factor for the (homogeneous) source-free contribution to the general solution of Maxwell's equations. Since classical electrodynamics can be solved while taking the homogenous source-free contribution in the solution as zero or non-zero, there are naturally two different theories of classical electrodynamics, one in which Planck's constant is taken as zero and one where it is taken as non-zero. The textbooks of classical electromagnetism present only the version in which Planck's constant is taken to vanish.

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.

Determination of intrinsic attenuation in the oceanic lithosphere-asthenosphere system

Science.gov (United States)

Takeuchi, Nozomu; Kawakatsu, Hitoshi; Shiobara, Hajime; Isse, Takehi; Sugioka, Hiroko; Ito, Aki; Utada, Hisashi

2017-12-01

We recorded P and S waves traveling through the oceanic lithosphere-asthenosphere system (LAS) using broadband ocean-bottom seismometers in the northwest Pacific, and we quantitatively separated the intrinsic (anelastic) and extrinsic (scattering) attenuation effects on seismic wave propagation to directly infer the thermomechanical properties of the oceanic LAS. The strong intrinsic attenuation in the asthenosphere obtained at higher frequency (~3 hertz) is comparable to that constrained at lower frequency (~100 seconds) by surface waves and suggests frequency-independent anelasticity, whereas the intrinsic attenuation in the lithosphere is frequency dependent. This difference in frequency dependence indicates that the strong and broad peak dissipation recently observed in the laboratory exists only in the asthenosphere and provides new insight into what distinguishes the asthenosphere from the lithosphere.

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)

Ultrasonic attenuation in rare-earth monoarsenides

Indian Academy of Sciences (India)

2015-11-27

Home; Journals; Pramana – Journal of Physics; Volume 86; Issue 6. Ultrasonic attenuation in rare-earth monoarsenides .... Proceedings of the International Workshop/Conference on Computational Condensed Matter Physics and Materials Science (IWCCMP-2015). Posted on November 27, 2015. Guest Editors: Anurag ...

Strong coupling constant extraction from high-multiplicity Z +jets observables

Science.gov (United States)

Johnson, Mark; Maître, Daniel

2018-03-01

We present a strong coupling constant extraction at next-to-leading order QCD accuracy using ATLAS Z +2 ,3,4 jets data. This is the first extraction using processes with a dependency on high powers of the coupling constant. We obtain values of the strong coupling constant at the Z mass compatible with the world average and with uncertainties commensurate with other next-to-leading order extractions at hadron colliders. Our most conservative result for the strong coupling constant is αS(MZ)=0.117 8-0.0043+0.0051 .

Vector and axial constants of the baryon decuplet

International Nuclear Information System (INIS)

Belyaev, V.M.; Blok, B.Y.; Kogan, Y.I.

1985-01-01

On the basis of the QCD sum rules for the polarization operator in external axial and vector fields we determine the vector and axial transition constants in the 3/2 + baryon decuplet. We show that the renormalization of the axial constant is due to the interaction of the external axial field with the quark condensate

Measuring Boltzmann's Constant with Carbon Dioxide

Science.gov (United States)

Ivanov, Dragia; Nikolov, Stefan

2013-01-01

In this paper we present two experiments to measure Boltzmann's constant--one of the fundamental constants of modern-day physics, which lies at the base of statistical mechanics and thermodynamics. The experiments use very basic theory, simple equipment and cheap and safe materials yet provide very precise results. They are very easy and…

Attenuation compensation for least-squares reverse time migration using the viscoacoustic-wave equation

KAUST Repository

Dutta, Gaurav

2014-10-01

Strong subsurface attenuation leads to distortion of amplitudes and phases of seismic waves propagating inside the earth. Conventional acoustic reverse time migration (RTM) and least-squares reverse time migration (LSRTM) do not account for this distortion, which can lead to defocusing of migration images in highly attenuative geologic environments. To correct for this distortion, we used a linearized inversion method, denoted as Qp-LSRTM. During the leastsquares iterations, we used a linearized viscoacoustic modeling operator for forward modeling. The adjoint equations were derived using the adjoint-state method for back propagating the residual wavefields. The merit of this approach compared with conventional RTM and LSRTM was that Qp-LSRTM compensated for the amplitude loss due to attenuation and could produce images with better balanced amplitudes and more resolution below highly attenuative layers. Numerical tests on synthetic and field data illustrated the advantages of Qp-LSRTM over RTM and LSRTM when the recorded data had strong attenuation effects. Similar to standard LSRTM, the sensitivity tests for background velocity and Qp errors revealed that the liability of this method is the requirement for smooth and accurate migration velocity and attenuation models.

Attenuation compensation for least-squares reverse time migration using the viscoacoustic-wave equation

KAUST Repository

Dutta, Gaurav; Schuster, Gerard T.

2014-01-01

Strong subsurface attenuation leads to distortion of amplitudes and phases of seismic waves propagating inside the earth. Conventional acoustic reverse time migration (RTM) and least-squares reverse time migration (LSRTM) do not account for this distortion, which can lead to defocusing of migration images in highly attenuative geologic environments. To correct for this distortion, we used a linearized inversion method, denoted as Qp-LSRTM. During the leastsquares iterations, we used a linearized viscoacoustic modeling operator for forward modeling. The adjoint equations were derived using the adjoint-state method for back propagating the residual wavefields. The merit of this approach compared with conventional RTM and LSRTM was that Qp-LSRTM compensated for the amplitude loss due to attenuation and could produce images with better balanced amplitudes and more resolution below highly attenuative layers. Numerical tests on synthetic and field data illustrated the advantages of Qp-LSRTM over RTM and LSRTM when the recorded data had strong attenuation effects. Similar to standard LSRTM, the sensitivity tests for background velocity and Qp errors revealed that the liability of this method is the requirement for smooth and accurate migration velocity and attenuation models.

DFT computations of the lattice constant, stable atomic structure and ...

African Journals Online (AJOL)

This paper presents the most stable atomic structure and lattice constant of Fullerenes (C60). FHI-aims DFT code was used to predict the stable structure and the computational lattice constant of C60. These were compared with known experimental structures and lattice constants of C60. The results obtained showed that ...

Iterative reconstruction with attenuation compensation from cone-beam projections acquired via nonplanar orbits

International Nuclear Information System (INIS)

Zeng, G.L.; Weng, Y.; Gullberg, G.T.

1997-01-01

Single photon emission computed tomography (SPECT) imaging with cone-beam collimators provides improved sensitivity and spatial resolution for imaging small objects with large field-of-view detectors. It is known that Tuy's cone-beam data sufficiency condition must be met to obtain artifact-free reconstructions. Even though Tuy's condition was derived for an attenuation-free situation, the authors hypothesize that an artifact-free reconstruction can be obtained even if the cone-beam data are attenuated, provided the imaging orbit satisfies Tuy's condition and the exact attenuation map is known. In the authors' studies, emission data are acquired using nonplanar circle-and-line orbits to acquire cone-beam data for tomographic reconstructions. An extended iterative ML-EM (maximum likelihood-expectation maximization) reconstruction algorithm is derived and used to reconstruct projection data with either a pre-acquired or assumed attenuation map. Quantitative accuracy of the attenuation corrected emission reconstruction is significantly improved

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

Active acoustic leak detection for LMFBR steam generator. Sound attenuation due to bubbles

International Nuclear Information System (INIS)

Kumagai, Hiromichi; Sakuma, Toshio

1995-01-01

In the steam generators (SG) of LMFBR, it is necessary to detect the leakage of water from tubes of heat exchangers as soon as it occurs. The active acoustic detection method has drawn general interest owing to its short response time and reduction of the influence of background noise. In this paper, the application of the active acoustic detection method for SG is proposed, and sound attenuation by bubbles is investigated experimentally. Furthermore, using the SG sector model, sound field characteristics and sound attenuation characteristics due to injection of bubbles are studied. It is clarified that the sound attenuation depends upon bubble size as well as void fraction, that the distance attenuation of sound in the SG model containing heat transfer tubes is 6dB for each two-fold increase of distance, and that emitted sound attenuates immediately upon injection of bubbles. (author)

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

Dynamical chiral symmetry breaking and pion decay constant

International Nuclear Information System (INIS)

Gogohia, V.Sh.; Kluge, Gy.

1991-08-01

Flavour non-singlet, chiral axial-vector Ward-Takahashi identity is investigated in the framework of dynamical chiral symmetry breaking. The use of the condition of stationarity for the bound-state amplitude is proposed in order to fully determine this quantity and the regular piece of the corresponding axial vertex. This makes it possible to express the pion decay constant in terms of the quark propagator variables only. An exact expression was found for the pion decay constant in current algebra and in Jackiw-Johnson representation as well. We also find a new expression for the pion decay constant in the Pagels-Stokar-Cornwall variables within the framework of Jackiw-Johnson representation. (author) 22 refs.; 2 figs

Design study on quasi-constant gradient accelerator structure

International Nuclear Information System (INIS)