WorldWideScience

Sample records for c-rich attenuating structure

  1. Molecular cloning and construction of the coding region for human acetylcholinesterase reveals a G + C-rich attenuating structure

    International Nuclear Information System (INIS)

    Soreq, H.; Ben-Aziz, R.; Prody, C.A.; Seidman, S.; Gnatt, A.; Neville, L.; Lieman-Hurwitz, J.; Lev-Lehman, E.; Ginzberg, D.; Lapidot-Lifson, Y.; Zakut, H.

    1990-01-01

    To study the primary structure of human acetylcholinesterase and its gene expression and amplification, cDNA libraries from human tissues expressing oocyte-translatable AcChoEase mRNA were constructed and screened with labeled oligodeoxynucleotide probes. Several cDNA clones were isolated that encoded a polypeptide with ≥50% identically aligned amino acids to Torpedo AcChoEase and human butyrylcholinesterase. However, these cDNA clones were all truncated within a 300-nucleotide-long G + C-rich region with a predicted pattern of secondary structure having a high Gibbs free energy downstream from the expected 5' end of the coding region. Screening of a genomic DNA library revealed the missing 5' domain. When ligated to the cDNA and constructed into a transcription vector, this sequence encoded a synthetic mRNA translated in microinjected oocytes into catalytically active AcChoEase with marked preference for acetylthiocholine over butyrylthiocholine as a substrate, susceptibility to inhibition by the AcChoEase inhibitor BW284C51, and resistance to the AcChoEase inhibitor tetraisopropylpyrophosphoramide. Blot hybridization of genomic DNA from different individuals carrying amplified AcChoEase genes revealed variable intensities and restriction patterns with probes from the regions upstream and downstream from the predicted G + C-rich structure. Thus, the human AcChoEase gene includes a putative G + C-rich attenuator domain and is subject to structural alterations in cases of AcChoEase gene amplification

  2. A G-C-rich palindromic structural motif and a stretch of single-stranded purines are required for optimal packaging of Mason-Pfizer monkey virus (MPMV) genomic RNA.

    Science.gov (United States)

    Jaballah, Soumeya Ali; Aktar, Suriya J; Ali, Jahabar; Phillip, Pretty Susan; Al Dhaheri, Noura Salem; Jabeen, Aayesha; Rizvi, Tahir A

    2010-09-03

    During retroviral RNA packaging, two copies of genomic RNA are preferentially packaged into the budding virus particles whereas the spliced viral RNAs and the cellular RNAs are excluded during this process. Specificity towards retroviral RNA packaging is dependent upon sequences at the 5' end of the viral genome, which at times extend into Gag sequences. It has earlier been suggested that the Mason-Pfizer monkey virus (MPMV) contains packaging sequences within the 5' untranslated region (UTR) and Gag. These studies have also suggested that the packaging determinants of MPMV that lie in the UTR are bipartite and are divided into two regions both upstream and downstream of the major splice donor. However, the precise boundaries of these discontinuous regions within the UTR and the role of the intervening sequences between these dipartite sequences towards MPMV packaging have not been investigated. Employing a combination of genetic and structural prediction analyses, we have shown that region "A", immediately downstream of the primer binding site, is composed of 50 nt, whereas region "B" is composed of the last 23 nt of UTR, and the intervening 55 nt between these two discontinuous regions do not contribute towards MPMV RNA packaging. In addition, we have identified a 14-nt G-C-rich palindromic sequence (with 100% autocomplementarity) within region A that has been predicted to fold into a structural motif and is essential for optimal MPMV RNA packaging. Furthermore, we have also identified a stretch of single-stranded purines (ssPurines) within the UTR and 8 nt of these ssPurines are duplicated in region B. The native ssPurines or its repeat in region B when predicted to refold as ssPurines has been shown to be essential for RNA packaging, possibly functioning as a potential nucleocapsid binding site. Findings from this study should enhance our understanding of the steps involved in MPMV replication including RNA encapsidation process. Copyright (c) 2010 Elsevier Ltd

  3. H2O Formation in C-rich AGB Winds

    NARCIS (Netherlands)

    Lombaert, R.; Decin, L.; Royer, P.; de Koter, A.; Cox, N.L.J.; De Ridder, J.; Khouri, T.; Agúndez, M.; Blommaert, J.A.D.L.; Gernicharo, J.; González-Alfonso, E.; Groenewegen, M.A.T.; Kerschbaum, F.; Neufeld, D.; Vandenbussche, B.; Waelkens, C.

    2015-01-01

    The Herschel detection of warm H2O vapor emission from C-rich winds of AGB stars challenges the current understanding of circumstellar chemistry. Two mechanisms have been invoked to explain warm H2O formation. In the first, penetration of UV interstellar radiation through a clumpy circumstellar

  4. Anelastic attenuation structure of the southern Aegean subduction area

    Science.gov (United States)

    Ventouzi, Chrisanthi; Papazachos, Constantinos; Papaioannou, Christos; Hatzidimitriou, Panagiotis

    2014-05-01

    The study of the anelastic attenuation structure plays a very important role for seismic wave propagation and provides not only valuable constraints for the Earth's interior (temperature, relative viscosity, slab dehydration and melt transport) but also significant information for the simulation of strong ground motions. In order to investigate the attenuation structure of the broader Southern Aegean subduction area, acceleration spectra of intermediate depth earthquakes produced from data provided by two local networks which operated in the area were used. More specifically, we employed data from approximately 400 intermediate-depth earthquakes, as these were recorded from the EGELADOS seismic monitoring project which consisted of 65 land stations and 24 OBS recorders and operated during 2005-2007, as well as data from the earlier installed CYCNET local network, which operated during 2002-2005. A frequency-independent path attenuation operator t* was computed for both P and S arrivals for each waveform, using amplitude spectra generated by the recorded data of the aforementioned networks. Initially, estimated P and S traveltimes were examined and modeled as a function of epicentral distance for different groups of focal depths, using data from the CYCNET network in order to obtain the expected arrival information when original arrival times were not available. Two approaches to assess the spectral-decay were adopted for t* determination. Initially, an automated approach was used, where t* was automatically calculated from the slope of the acceleration spectrum, assuming an ω2 source model for frequencies above the corner frequency, fc. Estimation of t* was performed in the frequency band of 0.2 to 25 Hz, using only spectra with a signal-to-noise ratio larger than 3 for a frequency range of at least 4Hz for P-waves and 1Hz for S-waves, respectively. In the second approach, the selection of the linearly-decaying part of the spectra where t* was calculated, was

  5. 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.

  6. 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

  7. Selective Alkylation of C-Rich Bulge Motifs in Nucleic Acids by Quinone Methide Derivatives.

    Science.gov (United States)

    Lönnberg, Tuomas; Hutchinson, Mark; Rokita, Steven

    2015-09-07

    A quinone methide precursor featuring a bis-cyclen anchoring moiety has been synthesized and its capacity to alkylate oligonucleotide targets quantified in the presence and absence of divalent metal ions (Zn(2+) , Ni(2+) and Cd(2+) ). The oligonucleotides were designed for testing the sequence and secondary structure specificity of the reaction. Gel electrophoretic analysis revealed predominant alkylation of C-rich bulges, regardless of the presence of divalent metal ions or even the bis-cyclen anchor. This C-selectivity appears to be an intrinsic property of the quinone methide electrophile as reflected by its reaction with an equimolar mixture of the 2'-deoxynucleosides. Only dA-N1 and dC-N3 alkylation products were detected initially and only the dC adduct persisted for detection under conditions of the gel electrophoretic analysis. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Crystallographic study of one turn of G/C-rich B-DNA.

    Science.gov (United States)

    Heinemann, U; Alings, C

    1989-11-20

    The DNA decamer d(CCAGGCCTGG) has been studied by X-ray crystallography. At a nominal resolution of 1.6 A, the structure was refined to R = 16.9% using stereochemical restraints. The oligodeoxyribonucleotide forms a straight B-DNA double helix with crystallographic dyad symmetry and ten base-pairs per turn. In the crystal lattice, DNA fragments stack end-to-end along the c-axis to form continuous double helices. The overall helical structure and, notably, the groove dimensions of the decamer are more similar to standard, fiber diffraction-determined B-DNA than A-tract DNA. A unique stacking geometry is observed at the CA/TG base-pair step, where an increased rotation about the helix axis and a sliding motion of the base-pairs along their long axes leads to a superposition of the base rings with neighboring carbonyl and amino functions. Three-center (bifurcated) hydrogen bonds are possible at the CC/GG base-pair steps of the decamer. In their common sequence elements, d(CCAGGCCTGG) and the related G.A mismatch decamer d(CCAAGATTGG) show very similar three-dimensional structures, except that d(CCAGGCCTGG) appears to have a less regularly hydrated minor groove. The paucity of minor groove hydration in the center of the decamer may be a general feature of G/C-rich DNA and explain its relative instability in the B-form of DNA.

  9. Contribution of the first K-homology domain of poly(C)-binding protein 1 to its affinity and specificity for C-rich oligonucleotides

    OpenAIRE

    Yoga, Yano M. K.; Traore, Daouda A. K.; Sidiqi, Mahjooba; Szeto, Chris; Pendini, Nicole R.; Barker, Andrew; Leedman, Peter J.; Wilce, Jacqueline A.; Wilce, Matthew C. J.

    2012-01-01

    Poly-C-binding proteins are triple KH (hnRNP K homology) domain proteins with specificity for single stranded C-rich RNA and DNA. They play diverse roles in the regulation of protein expression at both transcriptional and translational levels. Here, we analyse the contributions of individual αCP1 KH domains to binding C-rich oligonucleotides using biophysical and structural methods. Using surface plasmon resonance (SPR), we demonstrate that KH1 makes the most stable interactions with both RNA...

  10. 3-D seismic velocity and attenuation structures in the geothermal field

    Energy Technology Data Exchange (ETDEWEB)

    Nugraha, Andri Dian [Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institute of Technology Bandung, Jalan Ganesha No. 10 Bandung, 40132 (Indonesia); Syahputra, Ahmad [Geophyisical Engineering, Faculty of Mining and Petroleum Engineering, Institute of Technology Bandung, Jalan Ganesha No. 10 Bandung, 40132 (Indonesia); Fatkhan,; Sule, Rachmat [Applied Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institute of Technology Bandung, Jalan Ganesha No. 10 Bandung, 40132 (Indonesia)

    2013-09-09

    We conducted delay time tomography to determine 3-D seismic velocity structures (Vp, Vs, and Vp/Vs ratio) using micro-seismic events in the geothermal field. The P-and S-wave arrival times of these micro-seismic events have been used as input for the tomographic inversion. Our preliminary seismic velocity results show that the subsurface condition of geothermal field can be fairly delineated the characteristic of reservoir. We then extended our understanding of the subsurface physical properties through determining of attenuation structures (Qp, Qs, and Qs/Qp ratio) using micro-seismic waveform. We combined seismic velocities and attenuation structures to get much better interpretation of the reservoir characteristic. Our preliminary attanuation structures results show reservoir characterization can be more clearly by using the 3-D attenuation model of Qp, Qs, and Qs/Qp ratio combined with 3-D seismic velocity model of Vp, Vs, and Vp/Vs ratio.

  11. 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.

  12. S-wave attenuation structure beneath the northern Izu-Bonin arc

    Science.gov (United States)

    Takahashi, Tsutomu; Obana, Koichiro; Kodaira, Shuichi

    2016-04-01

    To understand temperature structure or magma distribution in the crust and uppermost mantle, it is essential to know their attenuation structure. This study estimated the 3-D S-wave attenuation structure in the crust and uppermost mantle at the northern Izu-Bonin arc, taking into account the apparent attenuation due to multiple forward scattering. In the uppermost mantle, two areas of high seismic attenuation (high Q -1) imaged beneath the volcanic front were mostly colocated with low-velocity anomalies. This coincidence suggests that these high- Q -1 areas in low-velocity zones are the most likely candidates for high-temperature regions beneath volcanoes. The distribution of random inhomogeneities indicated the presence of three anomalies beneath the volcanic front: Two were in high- Q -1 areas but the third was in a moderate- Q -1 area, indicating a low correlation between random inhomogeneities and Q -1. All three anomalies of random inhomogeneities were rich in short-wavelength spectra. The most probable interpretation of such spectra is the presence of volcanic rock, which would be related to accumulated magma intrusion during episodes of volcanic activity. Therefore, the different distributions of Q -1 and random inhomogeneities imply that the positions of hot regions in the uppermost mantle beneath this arc have changed temporally; therefore, they may provide important constraints on the evolutionary processes of arc crust and volcanoes.

  13. Study of attenuation structure for central Anatolia region, Turkey based on Keskin seismic array data

    Science.gov (United States)

    Semin, K. U.; Ozel, N. M.

    2011-12-01

    Central Anatolia is bounded in the north by the well-known north Anatolian fault system (NAFS) and on the south-southwest is bounded by the east Anatolian fault system (EAFS). The central area does not have major faults and acts as a single block moving westward. This region is not considered as seismically active as the NAFS or EAFS but the recent moderate-size Bala earthquakes (Ml=5.7, Ml= 5.5) on 20 and 27 December 2007 near the Tuz golu fault may be an indication of future seismic activity. In order to get a better picture of the crustal structure of this region we applied Coda Normalization method for the measurement of Qs-1 as a function of frequency for the frequencies 1.5, 3, 6, 8 Hz. 20 and 27 December 2007 Bala earthquakes (Ml magnitude 5.6 an 5.5) and their aftershocks recorded by the Keskin seismic array (International Monitoring System code BRTR) is analyzed in this study. Keskin seismic array has a small aperture circular design with 6 vertical short period and 1 broadband borehole seismometers. In addition, Multiple Lapse Time Window Analysis (MLTWA) method was applied to the data for the separation of intrinsic and scattering attenuation inm the region at the same frequencies. MLTWA method allowed a separation between the intrinsic attenuation and scattering attenuation. Preliminary results show a relatively low attenuation compared to western and eastern anatolia regions. This might be explained by the less seismicity in the region. A study of the regional and site attenuation of seismic waves of earthquakes in this area will contribute in predicting earthquake generated ground-motion and becomes vital in making decisions for earthquake regulations, building codes and to monitoring nuclear explosions.

  14. Contribution of the first K-homology domain of poly(C)-binding protein 1 to its affinity and specificity for C-rich oligonucleotides.

    Science.gov (United States)

    Yoga, Yano M K; Traore, Daouda A K; Sidiqi, Mahjooba; Szeto, Chris; Pendini, Nicole R; Barker, Andrew; Leedman, Peter J; Wilce, Jacqueline A; Wilce, Matthew C J

    2012-06-01

    Poly-C-binding proteins are triple KH (hnRNP K homology) domain proteins with specificity for single stranded C-rich RNA and DNA. They play diverse roles in the regulation of protein expression at both transcriptional and translational levels. Here, we analyse the contributions of individual αCP1 KH domains to binding C-rich oligonucleotides using biophysical and structural methods. Using surface plasmon resonance (SPR), we demonstrate that KH1 makes the most stable interactions with both RNA and DNA, KH3 binds with intermediate affinity and KH2 only interacts detectibly with DNA. The crystal structure of KH1 bound to a 5'-CCCTCCCT-3' DNA sequence shows a 2:1 protein:DNA stoichiometry and demonstrates a molecular arrangement of KH domains bound to immediately adjacent oligonucleotide target sites. SPR experiments, with a series of poly-C-sequences reveals that cytosine is preferred at all four positions in the oligonucleotide binding cleft and that a C-tetrad binds KH1 with 10 times higher affinity than a C-triplet. The basis for this high affinity interaction is finally detailed with the structure determination of a KH1.W.C54S mutant bound to 5'-ACCCCA-3' DNA sequence. Together, these data establish the lead role of KH1 in oligonucleotide binding by αCP1 and reveal the molecular basis of its specificity for a C-rich tetrad.

  15. Structure of nanoparticles in transformer oil-based magnetic fluids, anisotropy of acoustic attenuation

    International Nuclear Information System (INIS)

    Kúdelčík, Jozef; Bury, Peter; Kopčanský, Peter; Timko, Milan

    2015-01-01

    The anisotropy of acoustic attenuation in transformer oil-based magnetic fluids upon the external magnetic field was studied to discover the structure of nanoparticles. When a magnetic field is increased, the interaction between the external magnetic field and the magnetic moments of the nanoparticles leads to the aggregation of magnetic nanoparticles and following clusters formation. However, the temperature of magnetic fluids and the concentration of nanoparticles also have very important influence on the structural changes. The measurement of the dependence of the acoustic attenuation on the angle between the magnetic field direction and acoustic wave vector (anisotropy) can give the useful information about the structure of magnetic nanoparticles formations. In the present, the results of anisotropy measurements of the transformer oil-based magnetic fluids are described and using appropriate theory the basic parameters of clusters are calculated. On the basis of the performed calculations, the proportion of the acoustic wave energy used for excitation of the translational and rotational degrees of freedom was also established. - Highlights: • Nanoparticles formation in transformer oil-based magnetic fluids was investigated. • The anisotropy acoustic spectroscopy as the method of investigation was used. • The external conditions on the structure of magnetic fluids were studied. • The structure parameters using suitable theoretical model were determined

  16. Structure of nanoparticles in transformer oil-based magnetic fluids, anisotropy of acoustic attenuation

    Energy Technology Data Exchange (ETDEWEB)

    Kúdelčík, Jozef, E-mail: kudelcik@fyzika.uniza.sk [Department of Physics, University of Žilina, Univerzitná 1, 010 01 Žilina (Slovakia); Bury, Peter [Department of Physics, University of Žilina, Univerzitná 1, 010 01 Žilina (Slovakia); Kopčanský, Peter; Timko, Milan [Department of Magnetism, IEP SAS, Watsonova 47, 040 01 Košice (Slovakia)

    2015-08-15

    The anisotropy of acoustic attenuation in transformer oil-based magnetic fluids upon the external magnetic field was studied to discover the structure of nanoparticles. When a magnetic field is increased, the interaction between the external magnetic field and the magnetic moments of the nanoparticles leads to the aggregation of magnetic nanoparticles and following clusters formation. However, the temperature of magnetic fluids and the concentration of nanoparticles also have very important influence on the structural changes. The measurement of the dependence of the acoustic attenuation on the angle between the magnetic field direction and acoustic wave vector (anisotropy) can give the useful information about the structure of magnetic nanoparticles formations. In the present, the results of anisotropy measurements of the transformer oil-based magnetic fluids are described and using appropriate theory the basic parameters of clusters are calculated. On the basis of the performed calculations, the proportion of the acoustic wave energy used for excitation of the translational and rotational degrees of freedom was also established. - Highlights: • Nanoparticles formation in transformer oil-based magnetic fluids was investigated. • The anisotropy acoustic spectroscopy as the method of investigation was used. • The external conditions on the structure of magnetic fluids were studied. • The structure parameters using suitable theoretical model were determined.

  17. Trade-off of Elastic Structure and Q in Interpretations of Seismic Attenuation

    Science.gov (United States)

    Deng, Wubing; Morozov, Igor B.

    2017-10-01

    The quality factor Q is an important phenomenological parameter measured from seismic or laboratory seismic data and representing wave-energy dissipation rate. However, depending on the types of measurements and models or assumptions about the elastic structure, several types of Qs exist, such as intrinsic and scattering Qs, coda Q, and apparent Qs observed from wavefield fluctuations. We consider three general types of elastic structures that are commonly encountered in seismology: (1) shapes and dimensions of rock specimens in laboratory studies, (2) geometric spreading or scattering in body-, surface- and coda-wave studies, and (3) reflectivity on fine layering in reflection seismic studies. For each of these types, the measured Q strongly trades off with the (inherently limited) knowledge about the respective elastic structure. For the third of the above types, the trade-off is examined quantitatively in this paper. For a layered sequence of reflectors (e.g., an oil or gas reservoir or a hydrothermal zone), reflection amplitudes and phases vary with frequency, which is analogous to a reflection from a contrast in attenuation. We demonstrate a quantitative equivalence between phase-shifted reflections from anelastic zones and reflections from elastic layering. Reflections from the top of an elastic layer followed by weaker reflections from its bottom can appear as resulting from a low Q within or above this layer. This apparent Q can be frequency-independent or -dependent, according to the pattern of thin layering. Due to the layering, the interpreted Q can be positive or negative, and it can depend on source-receiver offsets. Therefore, estimating Q values from frequency-dependent or phase-shifted reflection amplitudes always requires additional geologic or rock-physics constraints, such as sparseness and/or randomness of reflectors, the absence of attenuation in certain layers, or specific physical mechanisms of attenuation. Similar conclusions about the

  18. Radar attenuation in Europa's ice shell: obstacles and opportunities for constraining shell thickness and thermal structure

    Science.gov (United States)

    Kalousova, Klara; Schroeder, Dustin M.; Soderlund, Krista M.; Sotin, Christophe

    2016-10-01

    With its strikingly young surface and possibly recent endogenic activity, Europa is one of the most exciting bodies within our Solar System and a primary target for spacecraft exploration. Future missions to Europa are expected to carry ice penetrating radar instruments which are powerful tools to investigate the subsurface thermophysical structure of its ice shell.Several authors have addressed the 'penetration depth' of radar sounders at icy moons, however, the concept and calculation of a single value penetration depth is a potentially misleading simplification since it ignores the thermal and attenuation structure complexity of a realistic ice shell. Here we move beyond the concept of a single penetration depth by exploring the variation in two-way radar attenuation for a variety of potential thermal structures of Europa's ice shell as well as for a low loss and high loss temperature-dependent attenuation model. The possibility to detect brines is also investigated.Our results indicate that: (i) for all ice shell thicknesses investigated (5-30 km), a nominal satellite-borne radar sounder will penetrate between 15% and 100% of the total thickness, (ii) the maximum penetration depth strongly varies laterally with the deepest penetration possible through the cold downwellings, (iii) the direct detection of the ice/ocean interface might be possible for shells of up to 15 km if the radar signal travels through the cold downwelling, (iv) even if the ice/ocean interface is not detected, the penetration through most of the shell could constrain the deep shell structure through the loss of signal, and (v) for all plausible ice shells the two-way attenuation to the eutectic point is ≤30 dB which shows a robust potential for longitudinal investigation of the ice shell's shallow structure.Part of this work has been performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. K.K. acknowledges support by the Grant Agency of the

  19. Attenuation tomography in the western central Andes: A detailed insight into the structure of a magmatic arc

    Science.gov (United States)

    Haberland, Christian; Rietbrock, Andreas

    2001-06-01

    High-quality data from 1498 local earthquakes recorded by the PISCO '94 (Proyecto de Investigatión Sismológica de la Cordillera Occidental, 1994) and ANCORP '96 (Andean Continental Research Project, 1996) temporary seismological networks allowed the detailed determination of the three-dimensional (3-D) attenuation structure (Qp-1) beneath the recent magmatic arc in the western central Andes (20° to 24°S). Assuming a frequency-independent Qp-1 in a frequency band between 1 and 30 Hz, whole path attenuation (t*) was estimated from the amplitude spectra of the P waves using spectral ratios and a spectral inversion technique. The damped least squares inversion (tomography) of the data reveals a complex attenuation structure. Crust and mantle of the forearc and subducting slab are generally characterized by low attenuation (Qp > 1000). Crust and mantle beneath the magmatic arc show elevated attenuation. The strongest anomaly of extremely low Qp is found in the crust between 22° and 23°S beneath the recent volcanic arc (Qp < 100). N-S variations can be observed: The western flank of the crustal attenuation anomaly follows the curved course of the volcanic front. North of 21°S the attenuation is less developed. In the northern part of the study area the low-Qp zone penetrates in the forearc mantle down to the subducting slab. In the south a deeper zone of high attenuation is resolved between 23° and 24°S directly above the subducting slab. Low Qp in the mantle correlates with earthquake clusters. The strong crustal attenuation is confined to the distribution of young ignimbrites and silicic volcanism and is interpreted as a thermally weakened zone with partial melts. The attenuation pattern in the upper mantle might reflect the variable extent of the asthenosphere and maps variations of subduction-related hydration processes in the mantle wedge from slab-derived fluids.

  20. Gamma-ray beam attenuation to assess the influence of soil texture on structure deformation

    International Nuclear Information System (INIS)

    Pires, L.F.; Bacchi, O.O.S.; Dias, N.M.P.

    2006-01-01

    Gamma-ray beam attenuation is a non-invasive technique that permits analysis of soil porosity without disturbing the region of interest of the core sample. The technique has as additional advantage to allow measurements point by point on a millimetric scale in contrast to other methodologies that are invasive and analyze the soil properties in the bulk sample volume. Soil porosity can be used as an important parameter to quantify soil structural damages, which affect soil aeration, water movement and retention. In this study, porosities of three soils different in texture were measured at various positions in order to analyze the impact of the sampling procedure on the structure of each particular soil texture. The gamma-ray attenuation system consisted of an 241 Am radioactive source having an activity of 3.7 GBq, collimated with cylindrical lead collimators of 2 mm diameter. The results obtained show the presence of dense regions near the edges of samples and that different soil textures can suffer distinct deformations at sampling. (author)

  1. Seismic velocity and attenuation structures at the top 400 km of the inner core

    Science.gov (United States)

    Yu, W.; Wen, L.; Niu, F.

    2002-12-01

    Recent seismic studies reveal an ``east-west" hemispherical difference in seismic velocity and attenuation in the top of the inner core [Niu and Wen, 2001, Wen and Niu, 2002]. The PKiKP-PKIKP observations they used only allowed them to constrain the seismic structure in the top 80 km of the inner core. The question now arises as such to what depth this hemispherical difference persists. To answer this question, we combine the PKiKP-PKIKP dataset and the PKPbc-PKIKP observations at the distance range of 147o-160o to study seismic velocity and attenuation structures in the top 400 km of the inner core along the ``equatorial paths" (the paths whose ray angles > 35o from the polar direction). We select PKPbc-PKIKP waveforms from recordings in the Global Seismic Network (GSN) and several dense regional seismic arrays. We choose recordings for events from 1990 to 2000 with simple source time functions, so only those of intermediate and deep earthquakes are used. The observed PKPbc-PKIKP differential travel times and PKIKP/PKPbc amplitude ratios exhibit an ``east-west" hemispherical difference. The PKPbc-PKIKP travel time residuals are about 0.7 second larger for those sampling the ``eastern" hemisphere than those sampling the ``western" hemisphere. The PKIKP/PKPbc amplitude ratios are generally smaller for those sampling the ``eastern" hemisphere. We construct two seismic velocity and attenuation models, with one for each ``hemisphere", by iteratively modeling the observed PKiKP-PKIKP waveforms, the PKPbc-PKIKP differential travel times and the PKIKP/PKPbc amplitude ratios. For the ``eastern" hemisphere, the observations indicate that the E1 velocity gradient and Q structure, inferred from the PKiKP-PKIKP observations sampling the top 80 km of the inner core, extend at least to 230 km inside the inner core. A change of velocity gradient and Q value is required in the deeper portion of the inner core. For the ``western" hemisphere, on the other hand, W2 velocity gradient

  2. Hornet cuticle - a composite structure comprised of a series of duplex lamellae attenuating toward the interior of the body

    NARCIS (Netherlands)

    Ishay, JS; Kirshboim, S; Steinberg, D; Kalicharan, D; Jongebloed, WL

    Our study deals with the ultramicroscopic structure of the yellow pigmented cuticular stripes on the abdomen of the oriental hornet Vespa orientalis (Hymenoptera, Vespinae). The abdominal cuticle is composed of numerous (more than 25) lamellae which progressively attenuate as one proceeds from the

  3. New data on the structure of shear wave attenuation field in the region of the Semipalatinsk test site

    International Nuclear Information System (INIS)

    Kopnichev, Yu.F.; Sokolova, I.N.

    2001-01-01

    Using the recordings of the chemical explosions in Kazakhstan, obtained by locally deployed stations, we have studied the structure of the attenuation field in the earth's crust and upper mantle in the areas of the Degelen and Balapan test sites. We have analyzed the characteristics of short-period coda envelopes at frequencies of 1.25 and 5 Hz. The study has shown that abnormally high S-wave attenuation is observed at the Balapan site in the depth range of 10-120 km, where two large fault zones pass. At the Degelen site, the attenuation for the same depth range is much weaker. However, Q values sharply increase at the depth over 200 km in the area of the Semipalatinsk test site. We suppose that spatial-temporal variations of the attenuation field structure are associated with a rise of juvenile fluids through the deep fault zones caused by the long and intensive influence of the explosions. Such a mechanism also allows us to explain the existence of a large-scale heat anomaly in the area of the northeastern Kazakhstan, including the Semipalatinsk test site. (author)

  4. Radar attenuation in Europa's ice shell: Obstacles and opportunities for constraining the shell thickness and its thermal structure

    Science.gov (United States)

    Kalousová, Klára; Schroeder, Dustin M.; Soderlund, Krista M.

    2017-03-01

    Young surface and possible recent endogenic activity make Europa one of the most exciting solar system bodies and a primary target for spacecraft exploration. Future Europa missions are expected to carry ice-penetrating radar instruments designed to investigate its subsurface thermophysical structure. Several authors have addressed the radar sounders' performance at icy moons, often ignoring the complex structure of a realistic ice shell. Here we explore the variation in two-way radar attenuation for a variety of potential thermal structures of Europa's shell (determined by reference viscosity, activation energy, tidal heating, surface temperature, and shell thickness) as well as for low and high loss temperature-dependent attenuation model. We found that (i) for all investigated ice shell thicknesses (5-30 km), the radar sounder will penetrate between 15% and 100% of the total thickness, (ii) the maximum penetration depth varies laterally, with deepest penetration possible through cold downwellings, (iii) direct ocean detection might be possible for shells of up to 15 km thick if the signal travels through cold downwelling ice or the shell is conductive, (iv) even if the ice/ocean interface is not directly detected, penetration through most of the shell could constrain the deep shell structure through returns from deep non-ocean interfaces or the loss of signal itself, and (v) for all plausible ice shells, the two-way attenuation to the eutectic point is ≲30 dB which shows a robust potential for longitudinal investigation of the ice shell's shallow thermophysical structure.

  5. Fluorine and Sodium in C-rich Low-metallicity Stars

    Science.gov (United States)

    Lucatello, Sara; Masseron, Thomas; Johnson, Jennifer A.; Pignatari, Marco; Herwig, Falk

    2011-03-01

    We present the N, O, F, and Na abundance and 12C/13C isotopic ratio measurements or upper limits for a sample of 10 C-rich, metal-poor giant stars: 8 enhanced in s-process (CEMP-s) elements and 2 poor in n-capture elements (CEMP-no). The abundances are derived from IR, K-band, high-resolution CRIRES@VLT obtained spectra. The metallicity of our sample ranges from [Fe/H] = -3.4 to -1.3. F abundance could be measured only in two CEMP-s stars. With [F/Fe] = 0.64, one is mildly F-overabundant, while the other is F-rich, at [F/Fe] = 1.44. For the remaining eight objects, including both CEMP-no stars in our sample, only upper limits on F abundance could be placed. Our measurements and upper limits show that there is a spread in the [F/C+N] ratio in CEMP-s stars as predicted by theory. Predictions from nucleosynthetic models for low-mass, low-metallicity asymptotic giant branch (AGB) stars account for the derived F abundances, while the upper limits on F content derived for most of the stars are lower than the predicted values. The measured Na content is accounted for by AGB models in the 1.25-1.75 M sun range, confirming that the stars responsible for the peculiar abundance pattern observed in CEMP-s stars are low-mass, low-metallicity AGB stars in agreement with the most accepted astrophysical scenario. We conclude that the mechanism of F production in current state-of-the-art low-metallicity low-mass AGB models needs further scrutiny and that F measurements in a larger number of metal-poor stars are needed to better constrain the models. Based on observations made with ESO Telescopes at Paranal Observatories under program ID 080.D-0606A. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center, funded by the National Aeronautics and Space Administration and the National Science Foundation.

  6. Using Earthquake Location and Coda Attenuation Analysis to Explore Shallow Structures Above the Socorro Magma Body, New Mexico

    Science.gov (United States)

    Schmidt, J. P.; Bilek, S. L.; Worthington, L. L.; Schmandt, B.; Aster, R. C.

    2017-12-01

    The Socorro Magma Body (SMB) is a thin, sill-like intrusion with a top at 19 km depth covering approximately 3400 km2 within the Rio Grande Rift. InSAR studies show crustal uplift patterns linked to SMB inflation with deformation rates of 2.5 mm/yr in the area of maximum uplift with some peripheral subsidence. Our understanding of the emplacement history and shallow structure above the SMB is limited. We use a large seismic deployment to explore seismicity and crustal attenuation in the SMB region, focusing on the area of highest observed uplift to investigate the possible existence of fluid/magma in the upper crust. We would expect to see shallower earthquakes and/or higher attenuation if high heat flow, fluid or magma is present in the upper crust. Over 800 short period vertical component geophones situated above the northern portion of the SMB were deployed for two weeks in 2015. This data is combined with other broadband and short period seismic stations to detect and locate earthquakes as well as to estimate seismic attenuation. We use phase arrivals from the full dataset to relocate a set of 33 local/regional earthquakes recorded during the deployment. We also measure amplitude decay after the S-wave arrival to estimate coda attenuation caused by scattering of seismic waves and anelastic processes. Coda attenuation is estimated using the single backscatter method described by Aki and Chouet (1975), filtering the seismograms at 6, 9 and 12 Hz center frequencies. Earthquakes occurred at 2-13 km depth during the deployment, but no spatial patterns linked with the high uplift region were observed over this short duration. Attenuation results for this deployment suggest Q ranging in values of 130 to 2000, averaging around Q of 290, comparable to Q estimates of other studies of the western US. With our dense station coverage, we explore attenuation over smaller scales, and find higher attenuation for stations in the area of maximum uplift relative to stations

  7. The deeper structure of the southern Dead Sea basin derived from neural network analysis of velocity and attenuation tomography

    Science.gov (United States)

    Braeuer, Benjamin; Haberland, Christian; Bauer, Klaus; Weber, Michael

    2014-05-01

    The Dead Sea basin is a pull-apart basin at the Dead Sea transform fault, the boundary between the African and the Arabian plates. Though the DSB has been studied for a long time, the available knowledge - based mainly on surface geology, drilling and seismic reflection surveys - gives only a partial picture of its shallow structure. Therefore, within the framework of the international DESIRE (DEad Sea Integrated REsearch) project, a dense temporary local seismological network was operated in the southern Dead Sea area. Within 18 month of recording 650 events were detected. In addition to an already published tomography study revealing the distribution of P velocities and the Vp/Vs ratios a 2D P-wave attenuation tomography (parameter Qp) was performed. The neural network technique of Self-organizing maps (SOM) is used for the joint interpretation of these three parameters (Vp, Vp/Vs, Qp). The resulting clusters in the petrophysical parameter space are assigned to the main lithological units below the southern part of the Dead Sea basin: (1) The basin sediments characterized by strong attenuation, high vp/vs ratios and low P velocities. (2) The pre-basin sediments characterized by medium to strong attenuation, low Vp/Vs ratios and medium P velocities. (3) The basement characterized by low to moderate attenuation, medium vp/vs ratios and high P velocities. Thus, the asymmetric southern Dead Sea basin is filled with basin sediments down to depth of 7 to 12 km. Below the basin sediments, the pre-basin sediments are extending to a depth between 13 and 18 km.

  8. Extraction of optical scattering parameters and attenuation compensation in optical coherence tomography images of multi-layered tissue structures

    DEFF Research Database (Denmark)

    Thrane, Lars; Frosz, Michael Henoch; Tycho, Andreas

    2004-01-01

    A recently developed analytical optical coherence tomography (OCT) model [Thrane et al., J. Opt. Soc. Am. A 17, 484 (2000)] allows the extraction of optical scattering parameters from OCT images, thereby permitting attenuation compensation in those images. By expanding this theoretical model, we...... have developed a new method for extracting optical scattering parameters from multilayered tissue structures in vivo. To verify this, we used a Monte Carlo (MC) OCT model as a numerical phantom to simulate the OCT signal for het-erogeneous multilayered tissue. Excellent agreement between the extracted......, and the results hold promise for expanding the functional imaging capabilities of OCT....

  9. Disturbance Attenuation of DC Voltage Droop Control Structures in a Multi-Terminal HVDC Grid

    DEFF Research Database (Denmark)

    Thams, Florian; Chatzivasileiadis, Spyros; Prieto-Araujo, Eduardo

    2017-01-01

    DC voltage droop control is seen as the preferred control structure for primary voltage control of future multiterminal HVDC systems. Different droop control structures have been proposed in literature which can be classified in eight categories. This paper contributes to an analysis of the distu......DC voltage droop control is seen as the preferred control structure for primary voltage control of future multiterminal HVDC systems. Different droop control structures have been proposed in literature which can be classified in eight categories. This paper contributes to an analysis...

  10. Three-dimensional Upper Crustal Velocity and Attenuation Structures of the Central Tibetan Plateau from Local Earthquake Tomography

    Science.gov (United States)

    Zhou, B.; Liang, X.; Lin, G.; Tian, X.; Zhu, G.; Mechie, J.; Teng, J.

    2017-12-01

    A series of V-shaped conjugate strike-slip faults are the most spectacular geologic features in the central Tibetan plateau. A previous study suggested that this conjugate strike-slip fault system accommodates the east-west extension and coeval north-south contraction. Another previous study suggested that the continuous convergence between the Indian and Eurasian continents and the eastward asthenospheric flow generated lithospheric paired general-shear (PGS) deformation, which then caused the development of conjugate strike-slip faults in central Tibet. Local seismic tomography can image three dimensional upper-crustal velocity and attenuation structures in central Tibet, which will provide us with more information about the spatial distribution of physical properties and compositional variations around the conjugate strike-slip fault zone. Ultimately, this information could improve our understanding of the development mechanism of the conjugate strike-slip fault system. In this study, we collected 6,809 Pg and 2,929 Sg arrival times from 414 earthquakes recorded by the temporary SANDWICH and permanent CNSN networks from November 2013 to November 2015. We also included 300 P and 17 S arrival times from 12 shots recorded by the INDEPTH III project during the summer of 1998 in the velocity tomography. We inverted for preliminary Vp and Vp/Vs models using the SIMUL2000 tomography algorithm, and then relocated the earthquakes with these preliminary velocity models. After that, we inverted for the final velocity models with these improved source locations and origin times. After the velocity inversion, we performed local attenuation tomography using t* measurements from the same dataset with an already existing approach. There are correlated features in the velocity and attenuation structures. From the surface to 10 km depth, the study area is dominated by high Vp and Qp anomalies. However, from 10 km to 20 km depth, there is a low Vp and Qp zone distributed along the

  11. Experimental analysis of the structure attenuation characteristics on engine noise by pseudo cylinder pressure excitation; Giji tonaiatsu kashin ni yoru engine kozo no soon tokusei hyoka

    Energy Technology Data Exchange (ETDEWEB)

    Ozawa, H; Nakada, T [Isuzu Advanced Engineering Center, Tokyo (Japan)

    1997-10-01

    The engine structure attenuation has been experimentally analyzed by the newly developed in-cylinder excitation system. It can reproduce the complete cylinder pressure in non-running engine conditions by adopting the hydraulic and the piezoelectric actuator. The structure attenuation measured in this system has a good coincidence with the ones measured in actually engine operating conditions, meanwhile the current method, which applied only high frequency components as the excitation pressure, was shown to have the unsatisfied agreement. As a result, the proposed system has been concluded to be very useful to estimate the engine noise characteristics in non-running conditions. 4 refs., 11 figs., 1 tab.

  12. Consensus positive position feedback control for vibration attenuation of smart structures

    Science.gov (United States)

    Omidi, Ehsan; Nima Mahmoodi, S.

    2015-04-01

    This paper presents a new network-based approach for active vibration control in smart structures. In this approach, a network with known topology connects collocated actuator/sensor elements of the smart structure to one another. Each of these actuators/sensors, i.e., agent or node, is enhanced by a separate multi-mode positive position feedback (PPF) controller. The decentralized PPF controlled agents collaborate with each other in the designed network, under a certain consensus dynamics. The consensus constraint forces neighboring agents to cooperate with each other such that the disagreement between the time-domain actuation of the agents is driven to zero. The controller output of each agent is calculated using state-space variables; hence, optimal state estimators are designed first for the proposed observer-based consensus PPF control. The consensus controller is numerically investigated for a flexible smart structure, i.e., a thin aluminum beam that is clamped at its both ends. Results demonstrate that the consensus law successfully imposes synchronization between the independently controlled agents, as the disagreements between the decentralized PPF controller variables converge to zero in a short time. The new consensus PPF controller brings extra robustness to vibration suppression in smart structures, where malfunctions of an agent can be compensated for by referencing the neighboring agents’ performance. This is demonstrated in the results by comparing the new controller with former centralized PPF approach.

  13. Tangshen Formula Attenuates Colonic Structure Remodeling in Type 2 Diabetic Rats

    DEFF Research Database (Denmark)

    Chen, Pengmin; Zhao, Jingbo; Zhang, Haojun

    2017-01-01

    Aim. This study investigated the effect and mechanism of the Chinese herbal medicine Tangshen Formula (TSF) on GI structure remodeling in the rat model of diabetes. Methods. Type 2 diabetic rats were used. Wet weight per unit length, layer thicknesses, levels of collagens I and III, nuclear factor...

  14. Tailored plasmon-induced transparency in attenuated total reflection response in a metal-insulator-metal structure.

    Science.gov (United States)

    Matsunaga, Kouki; Hirai, Yusuke; Neo, Yoichiro; Matsumoto, Takahiro; Tomita, Makoto

    2017-12-19

    We demonstrated tailored plasmon-induced transparency (PIT) in a metal (Au)-insulator (SiO 2 )-metal (Ag) (MIM) structure, where the Fano interference between the MIM waveguide mode and the surface plasmon polariton (SPP) resonance mode induced a transparency window in an otherwise opaque wavenumber (k) region. A series of structures with different thicknesses of the Ag layer were prepared and the attenuated total reflection (ATR) response was examined. The height and width of the transparency window, as well as the relevant k-domain dispersion, were controlled by adjusting the Ag layer thickness. To confirm the dependency of PIT on Ag layer thickness, we performed numerical calculations to determine the electric field amplitude inside the layers. The steep k-domain dispersion in the transparency window is capable of creating a lateral beam shift known as the Goos-Hänchen shift, for optical device and sensor applications. We also discuss the Fano interference profiles in a ω - k two-dimensional domain on the basis of Akaike information criteria.

  15. The binding of TIA-1 to RNA C-rich sequences is driven by its C-terminal RRM domain.

    Science.gov (United States)

    Cruz-Gallardo, Isabel; Aroca, Ángeles; Gunzburg, Menachem J; Sivakumaran, Andrew; Yoon, Je-Hyun; Angulo, Jesús; Persson, Cecilia; Gorospe, Myriam; Karlsson, B Göran; Wilce, Jacqueline A; Díaz-Moreno, Irene

    2014-01-01

    T-cell intracellular antigen-1 (TIA-1) is a key DNA/RNA binding protein that regulates translation by sequestering target mRNAs in stress granules (SG) in response to stress conditions. TIA-1 possesses three RNA recognition motifs (RRM) along with a glutamine-rich domain, with the central domains (RRM2 and RRM3) acting as RNA binding platforms. While the RRM2 domain, which displays high affinity for U-rich RNA sequences, is primarily responsible for interaction with RNA, the contribution of RRM3 to bind RNA as well as the target RNA sequences that it binds preferentially are still unknown. Here we combined nuclear magnetic resonance (NMR) and surface plasmon resonance (SPR) techniques to elucidate the sequence specificity of TIA-1 RRM3. With a novel approach using saturation transfer difference NMR (STD-NMR) to quantify protein-nucleic acids interactions, we demonstrate that isolated RRM3 binds to both C- and U-rich stretches with micromolar affinity. In combination with RRM2 and in the context of full-length TIA-1, RRM3 significantly enhanced the binding to RNA, particularly to cytosine-rich RNA oligos, as assessed by biotinylated RNA pull-down analysis. Our findings provide new insight into the role of RRM3 in regulating TIA-1 binding to C-rich stretches, that are abundant at the 5' TOPs (5' terminal oligopyrimidine tracts) of mRNAs whose translation is repressed under stress situations.

  16. Autism attenuates sex differences in brain structure: a combined voxel-based morphometry and diffusion tensor imaging study.

    Science.gov (United States)

    Beacher, F D; Minati, L; Baron-Cohen, S; Lombardo, M V; Lai, M-C; Gray, M A; Harrison, N A; Critchley, H D

    2012-01-01

    It has been proposed that autism spectrums condition may represent a form of extreme male brain (EMB), a notion supported by psychometric, behavioral, and endocrine evidence. Yet, limited data are presently available evaluating this hypothesis in terms of neuroanatomy. Here, we investigated sex-related anatomic features in adults with AS, a "pure" form of autism not involving major developmental delay. Males and females with AS and healthy controls (n = 28 and 30, respectively) were recruited. Structural MR imaging was performed to measure overall gray and white matter volume and to assess regional effects by means of VBM. DTI was used to investigate the integrity of the main white matter tracts. Significant interactions were found between sex and diagnosis in total white matter volume, regional gray matter volume in the right parietal operculum, and fractional anisotropy (FA) in the body of the CC, cingulum, and CR. Post hoc comparisons indicated that the typical sexual dimorphism found in controls, whereby males have larger FA and total white matter volume, was absent or attenuated in participants with AS. Our results point to a fundamental role of the factors that underlie sex-specific brain differentiation in the etiology of autism.

  17. Recoding structural glycoprotein E2 in classical swine fever virus (CSFV) produces complete virus attenuation in swine and protects infected animals against disease.

    Science.gov (United States)

    Velazquez-Salinas, Lauro; Risatti, Guillermo R; Holinka, Lauren G; O'Donnell, Vivian; Carlson, Jolene; Alfano, Marialexia; Rodriguez, Luis L; Carrillo, Consuelo; Gladue, Douglas P; Borca, Manuel V

    2016-07-01

    Controlling classical swine fever (CSF) mainly involves vaccination with live attenuated vaccines (LAV). Experimental CSFV LAVs has been lately developed through reverse genetics using several different approaches. Here we present that codon de-optimization in the major CSFV structural glycoprotein E2 coding region, causes virus attenuation in swine. Four different mutated constructs (pCSFm1-pCSFm4) were designed using various mutational approaches based on the genetic background of the highly virulent strain Brescia (BICv). Three of these constructs produced infectious viruses (CSFm2v, CSFm3v, and CSFm4v). Animals infected with CSFm2v presented a reduced and extended viremia but did not display any CSF-related clinical signs. Animals that were infected with CSFm2v were protected against challenge with virulent parental BICv. This is the first report describing the development of an attenuated CSFV experimental vaccine by codon usage de-optimization, and one of the few examples of virus attenuation using this methodology that is assessed in a natural host. Published by Elsevier Inc.

  18. Attenuation of stress waves in single and multi-layered structures. [mitigation of elastic and plastic stress waves during spacecraft landing

    Science.gov (United States)

    Yang, J. C. S.; Tsui, C. Y.

    1972-01-01

    Analytical and experimental studies were made of the attenuation of the stress waves during passage through single and multilayer structures. The investigation included studies on elastic and plastic stress wave propagation in the composites and those on shock mitigating material characteristics such as dynamic stress-strain relations and energy absorbing properties. The results of the studies are applied to methods for reducing the stresses imposed on a spacecraft during planetary or ocean landings.

  19. Structural and vibrational study of 8-hydroxyquinoline-2-carboxaldehyde isonicotinoyl hydrazone - A potential metal-protein attenuating compound (MPAC) for the treatment of Alzheimer's disease

    Science.gov (United States)

    de Freitas, Leonardo Viana; da Silva, Cecilia C. P.; Ellena, Javier; Costa, Luiz Antônio Sodré; Rey, Nicolás A.

    2013-12-01

    A comprehensive structural and vibrational study of the potential metal-protein attenuating compound 8-hydroxyquinoline-2-carboxaldehyde isonicotinoyl hydrazone is reported. X-ray diffraction data, as well as FT-IR and Raman frequencies, were compared with the respective theoretical values obtained from DFT calculations. Theory agrees well with experiment. In this context, an attempt of total assignment concerning the FT-IR and Raman spectra of the title compound was performed, shedding new light on previous partial assignments published elsewhere.

  20. Growing imbedded Ni3C-rich layer with sharp interfaces by means of ion beam mixing of C/Ni layers

    International Nuclear Information System (INIS)

    Barna, Arpad; Kotis, Laszlo; Labar, Janos; Sulyok, Attila; Toth, Attila L; Menyhard, Miklos; Panjan, Peter

    2011-01-01

    C/Ni bilayers of various layer thicknesses (20-40 nm) were ion bombarded using Ga + and Ni + projectiles of energies 20 and 30 keV. Ion bombardment resulted in the growth of a Ni 3 C rich layer with the following features: (a) sharp carbon/Ni 3 C rich layer interface, (b) the amount of Ni 3 C produced by the irradiation proportional to the square root of the fluence and dependent on the type of projectile, (c) good correlation between the distribution of vacancies produced by the ion bombardment and the distribution of Ni 3 C. The formation of the metastable Ni 3 C compound was explained by a vacancy-assisted process. The sharp interface is the consequence of a relaxation process removing the intermixed Ni from the carbon layer. The square root of fluence dependence of the thickness of the Ni 3 C-rich layer can be explained by a usual diffusion equation considering moving boundaries.

  1. Chemometric analysis of attenuated total reflectance infrared spectra of Proteus mirabilis strains with defined structures of LPS.

    Science.gov (United States)

    Zarnowiec, Paulina; Mizera, Andrzej; Chrapek, Magdalena; Urbaniak, Mariusz; Kaca, Wieslaw

    2016-07-01

    Proteus spp. strains are some of the most important pathogens associated with complicated urinary tract infections and bacteremia affecting patients with immunodeficiency and long-term urinary catheterization. For epidemiological purposes, various molecular typing methods have been developed for this pathogen. However, these methods are labor intensive and time consuming. We evaluated a new method of differentiation between strains. A collection of Proteus spp. strains was analyzed by attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectroscopy in the mid-infrared region. ATR FT-IR spectroscopy used in conjunction with a diamond ATR accessory directly produced the biochemical profile of the surface chemistry of bacteria. We conclude that a combination of ATR FT-IR spectroscopy and mathematical modeling provides a fast and reliable alternative for discrimination between Proteus isolates, contributing to epidemiological research. © The Author(s) 2016.

  2. Structurally designed attenuated subunit vaccines for S. aureus LukS-PV and LukF-PV confer protection in a mouse bacteremia model.

    Directory of Open Access Journals (Sweden)

    Hatice Karauzum

    Full Text Available Previous efforts towards S. aureus vaccine development have largely focused on cell surface antigens to induce opsonophagocytic killing aimed at providing sterile immunity, a concept successfully applied to other Gram-positive pathogens such as Streptococcus pneumoniae. However, these approaches have largely failed, possibly in part due to the remarkable diversity of the staphylococcal virulence factors such as secreted immunosuppressive and tissue destructive toxins. S. aureus produces several pore-forming toxins including the single subunit alpha hemolysin as well as bicomponent leukotoxins such as Panton-Valentine leukocidin (PVL, gamma hemolysins (Hlg, and LukED. Here we report the generation of highly attenuated mutants of PVL subunits LukS-PV and LukF-PV that were rationally designed, based on an octameric structural model of the toxin, to be deficient in oligomerization. The attenuated subunit vaccines were highly immunogenic and showed significant protection in a mouse model of S. aureus USA300 sepsis. Protection against sepsis was also demonstrated by passive transfer of rabbit immunoglobulin raised against LukS-PV. Antibodies to LukS-PV inhibited the homologous oligomerization of LukS-PV with LukF-PV as well heterologous oligomerization with HlgB. Importantly, immune sera from mice vaccinated with the LukS mutant not only inhibited the PMN lytic activity produced by the PVL-positive USA300 but also blocked PMN lysis induced by supernatants of PVL-negative strains suggesting a broad protective activity towards other bicomponent toxins. These findings strongly support the novel concept of an anti-virulence, toxin-based vaccine intended for prevention of clinical S. aureus invasive disease, rather than achieving sterile immunity. Such a multivalent vaccine may include attenuated leukotoxins, alpha hemolysin, and superantigens.

  3. Attenuation of LDHA expression in cancer cells leads to redox-dependent alterations in cytoskeletal structure and cell migration.

    Science.gov (United States)

    Arseneault, Robert; Chien, Andrew; Newington, Jordan T; Rappon, Tim; Harris, Richard; Cumming, Robert C

    2013-09-28

    Aerobic glycolysis, the preferential use of glycolysis even in the presence of oxygen to meet cellular metabolic demands, is a near universal feature of cancer. This unique type of metabolism is thought to protect cancer cells from damaging reactive oxygen species (ROS) produced in the mitochondria. Using the cancer cell line MDA-MB-435 it is shown that shRNA mediated knockdown of lactate dehydrogenase A (LDHA), a key mediator of aerobic glycolysis, results in elevated mitochondrial ROS production and a concomitant decrease in cell proliferation and motility. Redox-sensitive proteins affected by oxidative stress associated with LDHA knockdown were identified by Redox 2D-PAGE and mass spectrometry. In particular, tropomyosin (Tm) isoforms Tm4, Tm5NM1 and Tm5NM5, proteins involved in cell migration and cytoskeletal dynamics, exhibited changes in disulfide bonding and co-localized with peri-nuclear actin aggregates in LDHA knockdown cells. In contrast, treatment with the thiol-based antioxidant N-acetylcysteine promoted the relocalization of Tms to cortical actin microfilaments and partially rescued the migration defects associated with attenuated LDHA expression. These results suggest that aerobic glycolysis and reduced mitochondrial ROS production create an environment conducive to cytoskeletal remodeling; key events linked to the high cell motility associated with cancer. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  4. Insights into the structure and tectonic history of the southern South Island, New Zealand, from the 3-D distribution of P- and S-wave attenuation

    Science.gov (United States)

    Eberhart-Phillips, Donna; Reyners, Martin; Upton, Phaedra; Gubbins, David

    2018-05-01

    The Pacific-Australian plate boundary in the South Island of New Zealand is a transpressive boundary through continental lithosphere consisting of multiple terranes which were amalgamated during previous periods of subduction and plate reorganization. The style and locus of deformation within the present-day plate boundary is controlled by the mechanical behavior and distribution of these different lithospheric blocks. Geological studies are limited when it comes to illuminating lithospheric structure and rheology at depth. Imaging the 3-D seismic velocity and attenuation (1/Q), with distributed local earthquakes, helps unravel regional structure and variations in strength, fractures and fluids. We determine the 3-D distribution of Qp and Qs, which show much more variation than seismic velocity (Vp), underlining the utility of Q (1/attenuation). The Haast schist belt, previously shown as c. 25-km thick dry unit with moderate Vp and low Vp/Vs, is imaged with high Qs, and the highest Qs areas correlate with zones of higher grade schist. Below 25-km depth, the distribution of high Qp and Qs is markedly different from that of the overlying geological terranes. Both the strike and dip of the high Q regions indicate that they represent the subducted Hikurangi Plateau and its adjacent Cretaceous oceanic crust. The thickest part of the plateau, previously identified by Vp > 8.5 km/s from seismic tomography and P-wave precursors and associated with an eclogite layer at the base of the plateau, also has the highest Q. This confirms that the strong plateau extends southwestward as a narrow salient to the northern Fiordland subduction zone, where moderate-Q Eocene oceanic crust on the Australian plate is being subducted and bent to vertical. In the ductile crust, Q results suggest fluid saturation and elevated temperature conditions in the crustal root of the Southern Alps, and confirm that the shape of this crustal root is influenced by both the orientation and depth of the

  5. Attenuation in Superconducting Circular Waveguides

    Directory of Open Access Journals (Sweden)

    K. H. Yeap

    2016-09-01

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

  6. 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.

  7. 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.)

  8. 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.

  9. The chicken beta 2-microglobulin gene is located on a non-major histocompatibility complex microchromosome: a small, G+C-rich gene with X and Y boxes in the promoter

    DEFF Research Database (Denmark)

    Riegert, P; Andersen, R; Bumstead, N

    1996-01-01

    a similar genomic organization but smaller introns and higher G+C content than mammalian beta 2-microglobulin genes. The promoter region is particularly G+C-rich and contains, in addition to interferon regulatory elements, potential S/W, X, and Y boxes that were originally described for mammalian class II...... but not class I alpha or beta 2-microglobulin genes. There is a single chicken beta 2-microglobulin gene that has little polymorphism in the coding region. Restriction fragment length polymorphisms from Mhc homozygous lines, Mhc congenic lines, and backcross families, as well as in situ hybridization, show...

  10. 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...

  11. 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.

  12. 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)

  13. 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.

  14. Superação de dormência na qualidade de sementes e mudas: influência na produção de Senna multijuga (L. C. Rich. Irwin & Barneby Overcoming of dormancy in the quality of seeds and seedlings: influence in the production of Senna multijuga (L.C. Rich. Irwin & barneby

    Directory of Open Access Journals (Sweden)

    Graziela Piveta

    2010-01-01

    Full Text Available O objetivo deste trabalho foi determinar a qualidade fisiológica e sanitária de sementes de Senna multijuga(L. C. Rich. Irwin & Barneby relacionada aos métodos de superação de dormência e à interferência na produção de mudas. As sementes foram submetidas aos seguintes métodos: imersão em água fervente, as sementes foram imersas em água, com temperatura de 100°C, até esfriar, por 24 horas; escarificação ácida, onde as sementes foram imersas em ácido sulfúrico (H2SO4 a 90%, por 10 e 20 minutos, e testemunha (sem tratamento. Foram realizados os testes de sanidade, germinação, tetrazólio e avaliação da qualidade das mudas. O delineamento experimental foi inteiramente casualizado. Para a avaliação da germinação foi utilizado um esquema fatorial (4 X 2, com quatro métodos de superação de dormência X dois fotoperíodos, para os substratos rolo-de-papel e vermiculita. A escarificação ácida constituiu-se no método mais eficiente para a superação da dormência das sementes de Senna multijuga. Penicillium sp. e Aspergillus sp. tiveram sua incidência aumentada quando o tegumento foi danificado pela escarificação ácida por 20 minutos. O controle de Fusarium spp. aumentou gradativamente com o aumento do tempo de exposição ao ácido sulfúrico.The objective of this work was to determine the physiological and sanitary quality of Senna multijugaseeds related to the methods of dormancy overcoming and the influence on the seedlings quality. The seeds had been submitted to the following methods :immersion in water fervent, the seeds had been immersed in water, at 100°C, until cooling for 24 hours; acid escarification, where the seeds had been immersed in sulfuric acid (H2SO4 90%, for 10 and 20 minutes, and control (without treatment. The tests of sanity, germination and tetrazolium had been carried through, and were evaluated the quality of the seedlings. For the germination of the evaluation an factorial project was

  15. Role of primary substrate composition on microbial community structure and function and trace organic chemical attenuation in managed aquifer recharge systems

    KAUST Repository

    Li, Dong

    2014-03-26

    This study was performed to reveal the microbial community characteristics in simulated managed aquifer recharge (MAR), a natural water treatment system, under different concentrations and compositions of biodegradable dissolved organic carbon (BDOC) and further link these to the biotransformation of emerging trace organic chemicals (TOrCs). Two pairs of soil-column setups were established in the laboratory receiving synthetic feed solutions composed of different peptone/humic acid ratios and concentrations. Higher BDOC concentration resulted in lower microbial community diversity and higher relative abundance of Betaproteobacteria. Decreasing the peptone/humic acid ratio resulted in higher diversity of the community and higher relative abundances of Firmicutes, Planctomycetes, and Actinobacteria. The metabolic capabilities of microbiome involved in xenobiotics biodegradation were significantly promoted under lower BDOC concentration and higher humic acid content. Cytochrome P450 genes were also more abundant under these primary substrate conditions. Lower peptone/humic acid ratios also promoted the attenuation of most TOrCs. These results suggest that the primary substrate characterized by a more refractory character could increase the relative abundances of Firmicutes, Planctomycetes, and Actinobacteria, as well as associated cytochrome P450 genes, all of which should play important roles in the biotransformation of TOrCs in this natural treatment system. © 2014 Springer-Verlag.

  16. Role of primary substrate composition on microbial community structure and function and trace organic chemical attenuation in managed aquifer recharge systems.

    Science.gov (United States)

    Li, Dong; Alidina, Mazahirali; Drewes, Jörg E

    2014-06-01

    This study was performed to reveal the microbial community characteristics in simulated managed aquifer recharge (MAR), a natural water treatment system, under different concentrations and compositions of biodegradable dissolved organic carbon (BDOC) and further link these to the biotransformation of emerging trace organic chemicals (TOrCs). Two pairs of soil-column setups were established in the laboratory receiving synthetic feed solutions composed of different peptone/humic acid ratios and concentrations. Higher BDOC concentration resulted in lower microbial community diversity and higher relative abundance of Betaproteobacteria. Decreasing the peptone/humic acid ratio resulted in higher diversity of the community and higher relative abundances of Firmicutes, Planctomycetes, and Actinobacteria. The metabolic capabilities of microbiome involved in xenobiotics biodegradation were significantly promoted under lower BDOC concentration and higher humic acid content. Cytochrome P450 genes were also more abundant under these primary substrate conditions. Lower peptone/humic acid ratios also promoted the attenuation of most TOrCs. These results suggest that the primary substrate characterized by a more refractory character could increase the relative abundances of Firmicutes, Planctomycetes, and Actinobacteria, as well as associated cytochrome P450 genes, all of which should play important roles in the biotransformation of TOrCs in this natural treatment system.

  17. 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....

  18. 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.)

  19. Quantitative analysis of artifacts in 4D DSA: the relative contributions of beam hardening and scatter to vessel dropout behind highly attenuating structures

    Science.gov (United States)

    Hermus, James; Szczykutowicz, Timothy P.; Strother, Charles M.; Mistretta, Charles

    2014-03-01

    When performing Computed Tomographic (CT) image reconstruction on digital subtraction angiography (DSA) projections, loss of vessel contrast has been observed behind highly attenuating anatomy, such as dental implants and large contrast filled aneurysms. Because this typically occurs only in a limited range of projection angles, the observed contrast time course can potentially be altered. In this work, we have developed a model for acquiring DSA projections that models both the polychromatic nature of the x-ray spectrum and the x-ray scattering interactions to investigate this problem. In our simulation framework, scatter and beam hardening contributions to vessel dropout can be analyzed separately. We constructed digital phantoms with large clearly defined regions containing iodine contrast, bone, soft issue, titanium (dental implants) or combinations of these materials. As the regions containing the materials were large and rectangular, when the phantoms were forward projected, the projections contained uniform regions of interest (ROI) and enabled accurate vessel dropout analysis. Two phantom models were used, one to model the case of a vessel behind a large contrast filled aneurysm and the other to model a vessel behind a dental implant. Cases in which both beam hardening and scatter were turned off, only scatter was turned on, only beam hardening was turned on, and both scatter and beam hardening were turned on, were simulated for both phantom models. The analysis of this data showed that the contrast degradation is primarily due to scatter. When analyzing the aneurysm case, 90.25% of the vessel contrast was lost in the polychromatic scatter image, however only 50.5% of the vessel contrast was lost in the beam hardening only image. When analyzing the teeth case, 44.2% of the vessel contrast was lost in the polychromatic scatter image and only 26.2% of the vessel contrast was lost in the beam hardening only image.

  20. Pumpkin Seed Oil Attenuates Functional and Structural Disorders in Urogenital System of Male Albino Rats Induced by Whole Body Gamma Irradiation

    International Nuclear Information System (INIS)

    Rezk, R.G.; Darwish, M.R

    2012-01-01

    Pumpkin seeds have long been used for health benefits and the seed oil has been shown to contain active beneficial components that may protect from oxidative stress. The aim of the present study is to evaluate the modulator role of pumpkin seed oil (PSO) supplementation on gamma radiation induced changes in certain biochemical and histological abnormalities in both kidney and testes tissues. Male rats received 5Gy whole body gamma-irradiation delivered as 1 Gy day after day to result in a cumulative dose of 5 Gy. PSO was orally administered to rats (20mg/Kg body weight) for 20 consecutive days before irradiation and during the period of irradiation. On days seven and twenty one after the last irradiation dose, rats were sacrificed. Biochemical analysis in the serum revealed that PSO supplementation diminished the radiation-induced increase in the level of urea, creatinine , follicle stimulating hormone (FSH) and luteinizing hormone (LH). Significant amelioration of the radiation-induced decreases in calcium (Ca +2 ), potassium (K + ) and testosterone levels were also recorded. PSO administration has attenuated the toxic effects of radiation by decreasing the level of lipid peroxides measured as thiobarbituric acid reactive substances (TBARS) and increasing the activity of endogenous antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT) and the content of glutathione (GSH). Histological observations of photomicrographs of kidney sections of irradiated rats showed amorphoid glomeruli, renal sclerosis and high content of inflammatory cells and fibroblasts, hemorrhage in glomeruli, ruptured proximal and distal convoluted tubules. Examination of testis tissues showed disappearance of seminiferous tubules, ruptured tunica albuginea, and degeneration of interstitial cells. PSO supplementation has obviously improved the radiation-induced histopathological changes in both tissues. It could be concluded that PSO can be used as a useful adjunct for maintaining

  1. Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) Spectroscopy as an Analytical Method to Investigate the Secondary Structure of a Model Protein Embedded in Solid Lipid Matrices.

    Science.gov (United States)

    Zeeshan, Farrukh; Tabbassum, Misbah; Jorgensen, Lene; Medlicott, Natalie J

    2018-02-01

    Protein drugs may encounter conformational perturbations during the formulation processing of lipid-based solid dosage forms. In aqueous protein solutions, attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy can investigate these conformational changes following the subtraction of spectral interference of solvent with protein amide I bands. However, in solid dosage forms, the possible spectral contribution of lipid carriers to protein amide I band may be an obstacle to determine conformational alterations. The objective of this study was to develop an ATR FT-IR spectroscopic method for the analysis of protein secondary structure embedded in solid lipid matrices. Bovine serum albumin (BSA) was chosen as a model protein, while Precirol AT05 (glycerol palmitostearate, melting point 58 ℃) was employed as the model lipid matrix. Bovine serum albumin was incorporated into lipid using physical mixing, melting and mixing, or wet granulation mixing methods. Attenuated total reflection FT-IR spectroscopy and size exclusion chromatography (SEC) were performed for the analysis of BSA secondary structure and its dissolution in aqueous media, respectively. The results showed significant interference of Precirol ATO5 with BSA amide I band which was subtracted up to 90% w/w lipid content to analyze BSA secondary structure. In addition, ATR FT-IR spectroscopy also detected thermally denatured BSA solid alone and in the presence of lipid matrix indicating its suitability for the detection of denatured protein solids in lipid matrices. Despite being in the solid state, conformational changes occurred to BSA upon incorporation into solid lipid matrices. However, the extent of these conformational alterations was found to be dependent on the mixing method employed as indicated by area overlap calculations. For instance, the melting and mixing method imparted negligible effect on BSA secondary structure, whereas the wet granulation mixing method promoted

  2. 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)

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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)

  8. 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.

  9. 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.

  10. 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

  11. 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

  12. The attenuation of the periodic table

    International Nuclear Information System (INIS)

    Cook, N.D.

    1990-01-01

    Unique among models of nuclear structure, the face-centered-cubic (FCC) lattice model predicts the attenuation of the periodic table at Z < 110 and the impossibility of superheavy nuclei. The total binding energies of superheavy nuclei in the FCC model (109 < Z < 127) were calculated on the basis of parameters obtained from a least-squares best-fit for 914 nuclei (Z < 99). No indication of increased stability is found for any of the transuranic elements

  13. 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)

  14. 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

  15. Transport and attenuation of radiations

    CERN Document Server

    Nimal, J C

    2003-01-01

    This article treats of the calculation methods used for the dimensioning of the protections against radiations. The method consists in determining for a given point the flux of particles coming from a source at a given time. A strong attenuation (of about some few mu Sv.h sup - sup 1) is in general expected between the source and the areas accessible to the personnel or the public. The calculation has to take into account a huge number of radiation-matter interactions and to solve the integral-differential transport equation which links the particles flux to the source. Several methods exist from the simplified physical model with numerical developments to the more or less precise resolution of the transport equation. These methods allows also the calculation of the uncertainties of equivalent dose rates, heat sources, structure damages using the data covariances (efficient cross-sections, modeling, etc..): 1 - transport equation; 2 - Monte-Carlo method; 3 - semi-numerical methods S sub N; 4 - methods based o...

  16. 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

  17. 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...

  18. 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)

  19. Boundary layer attenuation in turbulent sodium flows

    International Nuclear Information System (INIS)

    Tenchine, D.

    1994-01-01

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

  20. Transient attenuation in optical fibers

    International Nuclear Information System (INIS)

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

    1984-01-01

    Low and high energy pulsed electron beams were used to generate radiation-induced transient attenuation in high-OH, Suprasil core, PCS fibers, demonstrating the energy dependence of the radiation damage and recovery mechanisms. A radiation resistant low-OH fiber was studied and its performance contrasted to that of high-OH materials. Several fibers with differing core compositions were also studied

  1. 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…

  2. 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...

  3. 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)

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

    Indian Academy of Sciences (India)

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

  5. Simulation on the shock attenuation behavior of coupled RHA and ...

    African Journals Online (AJOL)

    This paper presents the shock attenuation behavior of engineering materials namely Rolled Homogenous Armor (RHA) and sandwich composite when subject to blast loadings. Blast loading on sandwich composite structure and monolithic material are investigated using LSDYNA 3D with Arbitrary LagrangianEulerian ...

  6. Attenuation of Gamma Rays by Concrete . Lead Slag Composites

    International Nuclear Information System (INIS)

    Ismail, I.M.; Sweelam, M.H.; Zaghloul, Y.R.; Aly, H.F.

    2008-01-01

    Using of wastes and industrial by-products as concrete aggregate to be used as structural and radiation shielded material has increased in the recent years. Concrete was mixed with different amounts of lead slag extracted from recycling of the spent automotive batteries as fine aggregates. The lead slag was used as partial replacement of sand in the studied composites. The concrete composites obtained were characterized in terms of density, water absorption, porosity, compressive strength and attenuation of γ- rays with different energies. The attenuation coefficient and the half value thickness of the different matrices were calculated and discussed

  7. 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.

  8. 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.

  9. 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).

  10. Development of electrothermal actuation based planar variable optical attenuators (VOAs)

    International Nuclear Information System (INIS)

    Lee, Chengkuo; Yeh, J Andrew

    2006-01-01

    Several sorts of MEMS (Microelectromechanical Systems) based have been demonstrated by using electrostatic actuation scheme up to date. The comb drive and parallel plate are the two most common electrostatic actuators that have been well studied in variable optical attenuator (VOA) applications. In addition to the known retro-reflection type of optical attenuation being realized by our new devices driven by electrothermal actuators in present study, a novel planar tilted mirror with rotational and translation moving capability is proposed by using electrothermal actuators as well. Using electrothermal actuators to provide said planar tilted mirror with rotational and translational displacement has granted us a more efficient way to perform the light attenuation for in-plane structure. The static and transient characteristics of devices operated at ambient room temperature environment show good repeatability and stability

  11. 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

  12. Attenuation of thermal neutron through graphite

    International Nuclear Information System (INIS)

    Adib, M.; Ismaail, H.; Fathaallah, M.; Abbas, Y.; Habib, N.; Wahba, M.

    2004-01-01

    Calculation of the nuclear capture, thermal diffuse and Bragg scattering cross-sections as a function of graphite temperature and crystalline from for neutron energies from 1 me V< E<10 eV were carried out. Computer programs have been developed which allow calculation for the graphite hexagonal closed-pack structure in its polycrystalline form and pyrolytic one. I The calculated total cross-section for polycrystalline graphite were compared with the experimental values. An overall agreement is indicated between the calculated values and experimental ones. Agreement was also obtained for neutron cross-section measured for oriented pyrolytic graphite at room and liquid nitrogen temperatures. A feasibility study for use of graphite in powdered form as a cold neutron filter is details. The calculated attenuation of thermal neutrons through large mosaic pyrolytic graphite show that such crystals can be used effectively as second order filter of thermal neutron beams and that cooling improve their effectiveness

  13. Enhanced Attenuation Technologies: Passive Soil Vapor Extraction

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-03-15

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

  14. 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

  15. 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

  16. Monte Carlo simulation of diffuse attenuation coefficient in presence of non uniform profiles

    Digital Repository Service at National Institute of Oceanography (India)

    Desa, E; Desai, R.G.P.; Desa, B.A.E

    This paper presents a Monte Carlo simulation of the vertical depth structure of the downward attenuation coefficient (K sub(d)), and the irradiance reflectance (R) for a given profile of chlorophyll. The results are in quantitaive agreement...

  17. 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.

  18. SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION

    Energy Technology Data Exchange (ETDEWEB)

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

    2003-12-01

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

  19. 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.

  20. 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.

  1. Amplification and Attenuation across USArray using Ambient Noise Wavefront Tracking

    KAUST Repository

    Bowden, Daniel C.

    2017-11-15

    As seismic travel-time tomography continues to be refined using data from the vast USArray dataset, it is advantageous to also exploit the amplitude information carried by seismic waves. We use ambient noise cross correlation to make observations of surface-wave amplification and attenuation at shorter periods (8 – 32 seconds) than can be observed with only traditional teleseismic earthquake sources. We show that the wavefront tracking approach of [Lin et al., 2012a] can be successfully applied to ambient noise correlations, yielding results quite similar to those from earthquake observations at periods of overlap. This consistency indicates that the wavefront tracking approach is viable for use with ambient noise correlations, despite concerns of the inhomogeneous and unknown distribution of noise sources. The resulting amplification and attenuation maps correlate well with known tectonic and crustal structure; at the shortest periods, our amplification and attenuation maps correlate well with surface geology and known sedimentary basins, while our longest period amplitudes are controlled by crustal thickness and begin to probe upper mantle materials. These amplification and attenuation observations are sensitive to crustal materials in different ways than travel-time observations and may be used to better constrain temperature or density variations. We also value them as an independent means of describing the lateral variability of observed Rayleigh-wave amplitudes without the need for 3D tomographic inversions.

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

    Science.gov (United States)

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

    2018-03-01

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

  3. Attenuation vector in heterogeneous, weakly dissipative, anisotropic media

    Czech Academy of Sciences Publication Activity Database

    Červený, V.; Klimeš, L.; Pšenčík, Ivan

    2008-01-01

    Roč. 175, č. 1 (2008), s. 346-355 ISSN 0956-540X R&D Projects: GA ČR GA205/05/2182; GA ČR GA205/08/0332 Grant - others:GA ČR(CZ) GA205/07/0032 Institutional research plan: CEZ:AV0Z30120515 Keywords : seismic anisotropy * seismic attenuation * theoretical seismology * wave propagation Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 2.219, year: 2008

  4. 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

  5. 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 ...

  6. 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

  7. Backscatter and attenuation characterization of ventricular myocardium

    Science.gov (United States)

    Gibson, Allyson Ann

    2009-12-01

    This Dissertation presents quantitative ultrasonic measurements of the myocardium in fetal hearts and adult human hearts with the goal of studying the physics of sound waves incident upon anisotropic and inhomogeneous materials. Ultrasound has been used as a clinical tool to assess heart structure and function for several decades. The clinical usefulness of this noninvasive approach has grown with our understanding of the physical mechanisms underlying the interaction of ultrasonic waves with the myocardium. In this Dissertation, integrated backscatter and attenuation analyses were performed on midgestational fetal hearts to assess potential differences in the left and right ventricular myocardium. The hearts were interrogated using a 50 MHz transducer that enabled finer spatial resolution than could be achieved at more typical clinical frequencies. Ultrasonic data analyses demonstrated different patterns and relative levels of backscatter and attenuation from the myocardium of the left ventricle and the right ventricle. Ultrasonic data of adult human hearts were acquired with a clinical imaging system and quantified by their magnitude and time delay of cyclic variation of myocardial backscatter. The results were analyzing using Bayes Classification and ROC analysis to quantify potential advantages of using a combination of two features of cyclic variation of myocardial backscatter over using only one or the other feature to distinguish between groups of subjects. When the subjects were classified based on hemoglobin A1c, the homeostasis model assessment of insulin resistance, and the ratio of triglyceride to high-density lipoprotein-cholesterol, differences in the magnitude and normalized time delay of cyclic variation of myocardial backscatter were observed. The cyclic variation results also suggested a trend toward a larger area under the ROC curve when information from magnitude and time delay of cyclic variation is combined using Bayes classification than when

  8. 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...

  9. Hybrid DNA i-motif: Aminoethylprolyl-PNA (pC5) enhance the stability of DNA (dC5) i-motif structure.

    Science.gov (United States)

    Gade, Chandrasekhar Reddy; Sharma, Nagendra K

    2017-12-15

    This report describes the synthesis of C-rich sequence, cytosine pentamer, of aep-PNA and its biophysical studies for the formation of hybrid DNA:aep-PNAi-motif structure with DNA cytosine pentamer (dC 5 ) under acidic pH conditions. Herein, the CD/UV/NMR/ESI-Mass studies strongly support the formation of stable hybrid DNA i-motif structure with aep-PNA even near acidic conditions. Hence aep-PNA C-rich sequence cytosine could be considered as potential DNA i-motif stabilizing agents in vivo conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. 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

  11. Beta attenuation transmission system (BATS)

    Energy Technology Data Exchange (ETDEWEB)

    Hagan, R.C.; Fullbright, H.J.

    1977-01-01

    The beta attenuation transmission system (BATS) is an automated radiation gauge designed for quantitative measurement of component thickness in explosive detonators. The BATS was designed and built by Group M-1, the Nondestructive Testing Group, of the Los Alamos Scientific Laboratory to measure the areal thickness, in mg/cm/sup 2/, of a cylinder of high explosive (HE) enclosed within a plastic holder. The problem is to determine the density of the HE. A /sup 90/Sr source is collimated by a 0.25 x 1.59-mm slit, and the transmitted beta-particle flux is detected by a plastic scintillator, coupled to a photomultiplier tube. The detonator is transported through the radiation beam by a leadscrew, ballnut, stepping-motor combination. Continuous analog position data are available, derived from the output from a linear-actuated potentiometer attached to the scanner. A linear electrometer amplifies the detected signal, which is then integrated for a preselected time, to obtain the desired statistical accuracy. A microprocessor (..mu..P) is used to control the scanner position and to make the data readings at the assigned positions. The data are stored, and, at the completion of the scan, are processed into the desired format. The final answer is displayed to the operator or output to a peripheral device for permanent record. The characteristics of the radiation source, the collimator, the signal detection and conditioning, and the final results are described in detail. The scanner and the microprocessor control system are briefly outlined.

  12. Plasmodium falciparum: attenuation by irradiation

    International Nuclear Information System (INIS)

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

    1983-01-01

    The effect of irradiation on the in vitro growth of Plasmodium falciparum was investigated. The cultured malarial parasites at selected stages of development were exposed to gamma rays and the sensitivity of each stage was determined. The stages most sensitive to irradiation were the ring forms and the early trophozoites; late trophozoites were relatively insensitive. The greatest resistance was shown when parasites were irradiated at a time of transition from the late trophozoite and schizont stages to young ring forms. The characteristics of radiosensitive variation in the parasite cycle resembled that of mammalian cells. Growth curves of parasites exposed to doses of irradiation upto 150 gray had the same slope as nonirradiated controls but parasites which were exposed to 200 gray exhibited a growth curve which was less steep than that for parasites in other groups. Less than 10 organisms survived from the 10(6) parasites exposed to this high dose of irradiation; the possibility exists of obtaining radiation-attenuated P. falciparum

  13. Beta attenuation transmission system (BATS)

    International Nuclear Information System (INIS)

    Hagan, R.C.; Fullbright, H.J.

    1977-01-01

    The beta attenuation transmission system (BATS) is an automated radiation gauge designed for quantitative measurement of component thickness in explosive detonators. The BATS was designed and built by Group M-1, the Nondestructive Testing Group, of the Los Alamos Scientific Laboratory to measure the areal thickness, in mg/cm 2 , of a cylinder of high explosive (HE) enclosed within a plastic holder. The problem is to determine the density of the HE. A 90 Sr source is collimated by a 0.25 x 1.59-mm slit, and the transmitted beta-particle flux is detected by a plastic scintillator, coupled to a photomultiplier tube. The detonator is transported through the radiation beam by a leadscrew, ballnut, stepping-motor combination. Continuous analog position data are available, derived from the output from a linear-actuated potentiometer attached to the scanner. A linear electrometer amplifies the detected signal, which is then integrated for a preselected time, to obtain the desired statistical accuracy. A microprocessor (μP) is used to control the scanner position and to make the data readings at the assigned positions. The data are stored, and, at the completion of the scan, are processed into the desired format. The final answer is displayed to the operator or output to a peripheral device for permanent record. The characteristics of the radiation source, the collimator, the signal detection and conditioning, and the final results are described in detail. The scanner and the microprocessor control system are briefly outlined

  14. Attenuation characteristics of gypsum wallboard

    International Nuclear Information System (INIS)

    Christensen, Ralph C.; Sayeg, Joseph

    1978-01-01

    Increased cost of lead is promoting enhanced usage of common building materials for shielding in diagnostic medical and dental facilities where only a few half value layers (HVLs) are needed. We have measured attenuation of x-rays in gypsum wallboard as a function of kVp, filtration, and wallboard thickness. Our findings, obtained using a Victoreen 555 with an 0.1 DAS probe in poor geometry, are in agreement with the sparse data in the literature (Gross and McCullough (1977), Radiology 122: 825. Moos et al. (1961), Oral Surgery, Oral Medicine, and Oral Pathology 14: 569) but extend to thicker wall configurations and different kVp and filtration parameters. We conclude that gypsum wallboard as sole shielding material should be used with great caution. These findings are of value in maximizing the benefit/cost ratio for diagnostic shielding, and strengthen the conviction that, where used for shielding purposes, common building materials must be installed carefully and HVL-depth dependence considered thoroughly. (author)

  15. 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

  16. 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

  17. 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

  18. Compensation for photon attenuation in PET

    International Nuclear Information System (INIS)

    Chintu Chen; Ordonez, C.E.; Xiaolin Yu.

    1992-01-01

    CT/MR and PET images usually are not in registration spatially because of differences in the imaging setup. CT, MR and PET imaging parameters that are used regularly for brain studies in their institution are compared, in addition, because the patient orientations in CT/MR and PET scanners are not the same, slice centers are positioned differently relative to the patients anatomy. For application of the new idea of using structural information from CT or MR images in PET image reconstruction for attenuation correction, image registration is required as a first step so that one can obtain a corresponding anatomic map for any selected PET image plane. The authors chose to use the surface-matching technique developed in their laboratories for image registration because this method is retrospective and accurate. After the PET and CT/MR scans are registered, they reslice the CT/MR images along the planes of the PET images. The differences in slice thickness and slice separation, as well as in image resolution between various image modalities are to be considered

  19. A disorder-based strategy for tunable, broadband wave attenuation

    Science.gov (United States)

    Zhang, Weiting; Celli, Paolo; Cardella, Davide; Gonella, Stefano

    2017-04-01

    One of the most daunting limitations of phononic crystals and acoustic/elastic metamaterials is their passivity: a given configuration is bound to display its phononic properties only around its design point, i.e., working at some pre-determined operating conditions. In the past decade, this shortcoming has inspired the design of phononic media with tunable wave characteristics; noteworthy results have been obtained through a family of methodologies involving shunted piezoelectric elements. Shunting a piezoelectric element means connecting it to a passive electric circuit; tunability stems from the ability to modify the effective mechanical properties of the piezoelectric medium by modifying the circuit characteristics. One of the most popular shunting circuits is the resistor-inductor, which allows the patch-and-shunt system to behave as an electromechanical resonator. A common motif among the works employing shunted piezos for phononic control is periodicity: the patches are typically periodically placed in the domain and the circuits are identically tuned. The objective of this work is to demonstrate that the wave attenuation performance of structures with shunted piezoelectric patches can be improved by leveraging notions of organized disorder. Based on the idea of rainbow trapping broadband wave attenuation obtained by tuning an array of resonators at distinct neighboring frequencies we design and test an electromechanical waveguide structure capable of attenuating waves over broad frequency ranges. In order to emphasize the fact that periodicity is not a binding requirement when working with RL shunts (which induce locally resonant bandgaps), we report on the performance of random arrangements of patches. In an attempt to demonstrate the tunability attribute of our strategy, we take advantage of the reconfigurability of the circuits to show how a single waveguide can attenuate both waves and vibrations over different frequency ranges.

  20. 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.

  1. Structuralism.

    Science.gov (United States)

    Piaget, Jean

    Provided is an overview of the analytical method known as structuralism. The first chapter discusses the three key components of the concept of a structure: the view of a system as a whole instead of so many parts; the study of the transformations in the system; and the fact that these transformations never lead beyond the system but always…

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

    Directory of Open Access Journals (Sweden)

    Alexander A. Golyakhov

    2018-05-01

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

  3. 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.

  4. Dexmedetomidine in premedication to attenuate the acute ...

    African Journals Online (AJOL)

    Background: The choice of anaesthetic agent for electroconvulsive therapy (ECT) depends on seizure duration, haemodynamic ... and infarction. To attenuate this acute ... scheduled for ECT, physical status ASA I and II, age between 18 and.

  5. 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

  6. 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

  7. 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.)

  8. 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...

  9. 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).

  10. 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)

  11. Mechanisms of geometrical seismic attenuation

    Directory of Open Access Journals (Sweden)

    Igor B. Morozov

    2011-07-01

    Full Text Available In several recent reports, we have explained the frequency dependence of the apparent seismic quality-factor (Q observed in many studies according to the effects of geometrical attenuation, which was defined as the zero-frequency limit of the temporal attenuation coefficient. In particular, geometrical attenuation was found to be positive for most waves traveling within the lithosphere. Here, we present three theoretical models that illustrate the origin of this geometrical attenuation, and we investigate the causes of its preferential positive values. In addition, we discuss the physical basis and limitations of both the conventional and new attenuation models. For waves in media with slowly varying properties, geometrical attenuation is caused by variations in the wavefront curvature, which can be both positive (for defocusing and negative (for focusing. In media with velocity/density contrasts, incoherent reflectivity leads to geometrical-attenuation coefficients which are proportional to the mean squared reflectivity and are always positive. For «coherent» reflectivity, the geometrical attenuation is approximately zero, and the attenuation process can be described according to the concept of «scattering Q». However, the true meaning of this parameter is in describing the mean reflectivity within the medium, and not that of the traditional resonator quality factor known in mechanics. The general conclusion from these models is that non-zero and often positive levels of geometrical attenuation are common in realistic, heterogeneous media, both observationally and theoretically. When transformed into the conventional Q-factor form, this positive geometrical attenuation leads to Q values that quickly increase with frequency. These predictions show that the positive frequency-dependent Q observed in many datasets might represent artifacts of the transformations of the attenuation coefficients into Q.

  1. 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

  2. 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)

  3. 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

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

    International Nuclear Information System (INIS)

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

    2008-01-01

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

  5. 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.

  6. Controlled Attenuation Parameter And Alcoholic Hepatic Steatosis

    DEFF Research Database (Denmark)

    Thiele, Maja; Rausch, Vanessa; Fluhr, Gabriele

    2018-01-01

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

  7. Heat-accelerated radioinactivation of attenuated poliovirus

    International Nuclear Information System (INIS)

    Dugan, V.L.; Trujillo, R.

    1975-01-01

    Attenuated poliovirus is inactivated in a synergistic manner when exposed simultaneously to heat and ionizing radiation. The synergistic response is observed in both the thermally labile and stable forms of the virus. A three-term kinetic model may be used to describe the inactivation response of the virus in a thermal and/or ionizing radiation environment. (orig.) [de

  8. 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 ...

  9. Anethum Graveolens Linn (Umbelliferae) Extract Attenuates Stress ...

    African Journals Online (AJOL)

    Anethum Graveolens Linn (Umbelliferae) Extract Attenuates Stress-induced Urinary Biochemical Changes and Improves Cognition in Scopolamineinduced Amnesic Rats. ... Conclusion: The aqueous extract of A. graveolens exhibited significant anti-stress, antioxidant and memory enhancing activities. The study provides a ...

  10. Electron attenuation characteristics of LiF

    Energy Technology Data Exchange (ETDEWEB)

    Paliwal, B R [Wisconsin Univ., Madison (USA). Div. of Clinical Oncology; Almond, P R

    1976-08-01

    The results of a study, indicating the exponential nature of the attenuation of electrons in LiF, are reported. This conclusion holds good not only for the monoenergetic electrons obtained from several pure ..beta.. emitters but also for the high energy electron beams delivered by radiotherapy facilities.

  11. Microwave attenuation with composite of copper microwires

    International Nuclear Information System (INIS)

    Gorriti, A.G.; Marin, P.; Cortina, D.; Hernando, A.

    2010-01-01

    It is shown that copper microwires composite media attenuates microwave reflection of metallic surfaces. We show how the distance to the metallic surface, as well as the length and volume fraction of microwires, determine the frequency of maximum absorption and the return loss level. Furthermore, we were able to fit the experimental results with a theoretical model based on Maxwell-Garnett mixing formula.

  12. Microwave attenuation with composite of copper microwires

    Energy Technology Data Exchange (ETDEWEB)

    Gorriti, A.G.; Marin, P. [Instituto de Magnetismo Aplicado, (UCM-ADIF-CSIC) and Departamento de Fisica de Materiales (UCM). P.O. Box 155, Las Rozas, Madrid 28230 (Spain); Cortina, D. [Micromag S.L., Las Rozas, Madrid 28230 (Spain); Hernando, A., E-mail: antonio.hernando@adif.e [Instituto de Magnetismo Aplicado, (UCM-ADIF-CSIC) and Departamento de Fisica de Materiales (UCM). P.O. Box 155, Las Rozas, Madrid 28230 (Spain); Micromag S.L., Las Rozas, Madrid 28230 (Spain)

    2010-05-15

    It is shown that copper microwires composite media attenuates microwave reflection of metallic surfaces. We show how the distance to the metallic surface, as well as the length and volume fraction of microwires, determine the frequency of maximum absorption and the return loss level. Furthermore, we were able to fit the experimental results with a theoretical model based on Maxwell-Garnett mixing formula.

  13. Touch Attenuates Infants' Physiological Reactivity to Stress

    Science.gov (United States)

    Feldman, Ruth; Singer, Magi; Zagoory, Orna

    2010-01-01

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

  14. Attenuation Model Using the Large-N Array from the Source Physics Experiment

    Science.gov (United States)

    Atterholt, J.; Chen, T.; Snelson, C. M.; Mellors, R. J.

    2017-12-01

    The Source Physics Experiment (SPE) consists of a series of chemical explosions at the Nevada National Security Site. SPE seeks to better characterize the influence of subsurface heterogeneities on seismic wave propagation and energy dissipation from explosions. As a part of this experiment, SPE-5, a 5000 kg TNT equivalent chemical explosion, was detonated in 2016. During the SPE-5 experiment, a Large-N array of 996 geophones (half 3-component and half z-component) was deployed. This array covered an area that includes loosely consolidated alluvium (weak rock) and weathered granite (hard rock), and recorded the SPE-5 explosion as well as 53 weight drops. We use these Large-N recordings to develop an attenuation model of the area to better characterize how geologic structures influence source energy partitioning. We found a clear variation in seismic attenuation for different rock types: high attenuation (low Q) for alluvium and low attenuation (high Q) for granite. The attenuation structure correlates well with local geology, and will be incorporated into the large simulation effort of the SPE program to validate predictive models. (LA-UR-17-26382)

  15. 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.

  16. 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

  17. 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

  18. Lateral variation of seismic attenuation in Sikkim Himalaya

    Science.gov (United States)

    Thirunavukarasu, Ajaay; Kumar, Ajay; Mitra, Supriyo

    2017-01-01

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

  19. Boundary attenuation angles for inhomogeneous plane waves in anisotropic dissipative media

    Czech Academy of Sciences Publication Activity Database

    Červený, V.; Pšenčík, Ivan

    2011-01-01

    Roč. 76, č. 3 (2011), WA51-WA62 ISSN 0016-8033 R&D Projects: GA ČR(CZ) GAP210/11/0117 Institutional research plan: CEZ:AV0Z30120515 Keywords : attenuation angles * seismic waves * seismic anisotropy Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.418, year: 2011

  20. Coda attenuation analysis in the West Bohemia/Vogtland earthquake swarm area

    Czech Academy of Sciences Publication Activity Database

    Bachura, M.; Fischer, Tomáš

    2016-01-01

    Roč. 173, č. 2 (2016), s. 425-437 ISSN 0033-4553 R&D Projects: GA ČR GAP210/12/2336; GA MŠk LM2010008 Institutional support: RVO:67985530 Keywords : seismic coda * attenuation * Q quality factor Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.591, year: 2016

  1. 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

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

    Science.gov (United States)

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

    2008-10-01

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

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

    International Nuclear Information System (INIS)

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

    2008-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-07-01

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

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

    International Nuclear Information System (INIS)

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

    2010-01-01

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

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

    International Nuclear Information System (INIS)

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

    2017-01-01

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

  7. Overview of recent developments in attenuation models

    International Nuclear Information System (INIS)

    Riera, J.D.

    2001-01-01

    Attenuation equations predict features of the seismic motion, such as the horizontal and vertical peak ground accelerations (PGA), the peak ground velocities (PGV) and the 5% damped spectral acceleration response (SA), in terms of the earthquake magnitude and distance from source to site. Occasionally other factors, like the type of faulting, are considered in the attenuation expressions. An overview of recent developments in this field is presented in the paper, including a discussion of the applicability of various models for short source to site distances. In such a case, i.e. in the neighbourhood of the epicentral region, which is of utmost importance in Nuclear Power Plant applications, the use of two parameters to define the earthquake size is suggested, instead of the single parameter, a magnitude scale. Recent evidence of the importance in such situations of so-called directivity effects, which require a more complete description of the focal mechanism, completes the paper. (author)

  8. P300 is attenuated during dissociative episodes.

    Science.gov (United States)

    Kirino, Eiji

    2006-02-01

    The present study examined the pathophysiology of dissociative phenomena using the P300 component of event-related potentials, quantitative electroencephalography (QEEG), and morphology measures of computed tomography scan. Event-related potentials during an auditory oddball paradigm and QEEG in resting state were recorded. Patients exhibited attenuation of P300 amplitudes compared with controls during dissociative episodes, but exhibited recovery to control levels in remission. Patients had a larger Sylvian fissure-brain ratio than did controls. QEEG findings revealed no significant differences between the patients and controls or between episodes and remission in the patient group. Attenuation of the P300 can be interpreted as the result of a negative feedback loop from the medial temporal lobe to the cortex, which decreases the amount of information flow, allocation of attentional resources, and updating of working memory to avoid both excessive long-term memory system activity in medial temporal lobe and resurgence of affect-laden memories.

  9. 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.

  10. 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

  11. 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

  12. Increasing low frequency sound attenuation using compounded single layer of sonic crystal

    Science.gov (United States)

    Gulia, Preeti; Gupta, Arpan

    2018-05-01

    Sonic crystals (SC) are man-made periodic structures where sound hard scatterers are arranged in a crystalline manner. SC reduces noise in a particular range of frequencies called as band gap. Sonic crystals have a promising application in noise shielding; however, the application is limited due to the size of structure. Particularly for low frequencies, the structure becomes quite bulky, restricting its practical application. This paper presents a compounded model of SC, which has the same overall area and filling fraction but with increased low frequency sound attenuation. Two cases have been considered, a three layer SC and a compounded single layer SC. Both models have been analyzed using finite element simulation and plane wave expansion method. Band gaps for periodic structures have been obtained using both methods which are in good agreement. Further, sound transmission loss has been evaluated using finite element method. The results demonstrate the use of compounded model of Sonic Crystal for low frequency sound attenuation.

  13. Phonic Attenuation due to Screen-Barriers

    Directory of Open Access Journals (Sweden)

    Vasile Bacria

    2011-10-01

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

  14. Attenuation and scatter correction in SPECT

    International Nuclear Information System (INIS)

    Pant, G.S.; Pandey, A.K.

    2000-01-01

    While passing through matter, photons undergo various types of interactions. In the process, some photons are completely absorbed, some are scattered in different directions with or without any change in their energy and some pass through unattenuated. These unattenuated photons carry the information with them. However, the image data gets corrupted with attenuation and scatter processes. This paper deals with the effect of these two processes in nuclear medicine images and suggests the methods to overcome them

  15. Natural attenuation of biogas in landfill covers

    International Nuclear Information System (INIS)

    Cossu, R.; Privato, A.; Raga, R.

    2005-01-01

    In the risk evaluation of uncontrolled biogas emissions from landfills, the process of natural attenuation in landfill covers assumes a very important role. The capacity of biogas oxidation in the cover soils seems to be the most important control to mitigate the biogas emission during the aftercare period when the biogas collection system might fail. In the present paper laboratory experiences on lab columns to study the biogas oxidation are discussed [it

  16. Radiation attenuation gauge with magnetically coupled source

    International Nuclear Information System (INIS)

    Wallace, S.A.

    1978-01-01

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

  17. Wave attenuation charcteristics of tethered float system

    Digital Repository Service at National Institute of Oceanography (India)

    Vethamony, P.

    incident wave height transmitted wave height G wave number float mass number of rows of floats drag power transmitted wave power incident wave power 111 112 P. Vethamony float radius wave period time velocity and acceleration of fluid... particles, respectively wave attenuation in percentage displacement, velocity and acceleration of float, respectively amplitude of float displacement added mass damping coefficient fluid particle displacement amplitude of fluid particle displacement...

  18. Understanding pyrotechnic shock dynamics and response attenuation over distance

    Science.gov (United States)

    Ott, Richard J.

    Pyrotechnic shock events used during stage separation on rocket vehicles produce high amplitude short duration structural response that can lead to malfunction or degradation of electronic components, cracks and fractures in brittle materials, local plastic deformation, and can cause materials to experience accelerated fatigue life. These transient loads propagate as waves through the structural media losing energy as they travel outward from the source. This work assessed available test data in an effort to better understand attenuation characteristics associated with wave propagation and attempted to update a historical standard defined by the Martin Marietta Corporation in the late 1960's using out of date data acquisition systems. Two data sets were available for consideration. The first data set came from a test that used a flight like cylinder used in NASA's Ares I-X program, and the second from a test conducted with a flat plate. Both data sets suggested that the historical standard was not a conservative estimate of shock attenuation with distance, however, the variation in the test data did not lend to recommending an update to the standard. Beyond considering attenuation with distance an effort was made to model the flat plate configuration using finite element analysis. The available flat plate data consisted of three groups of tests, each with a unique charge density linear shape charge (LSC) used to cut an aluminum plate. The model was tuned to a representative test using the lowest charge density LSC as input. The correlated model was then used to predict the other two cases by linearly scaling the input load based on the relative difference in charge density. The resulting model predictions were then compared with available empirical data. Aside from differences in amplitude due to nonlinearities associated with scaling the charge density of the LSC, the model predictions matched the available test data reasonably well. Finally, modeling best

  19. Broadband Vibration Attenuation Using Hybrid Periodic Rods

    Directory of Open Access Journals (Sweden)

    S. Asiri

    2008-12-01

    Full Text Available This paper presents both theoretically and experimentally a new kind of a broadband vibration isolator. It is a table-like system formed by four parallel hybrid periodic rods connected between two plates. The rods consist of an assembly of periodic cells, each cell being composed of a short rod and piezoelectric inserts. By actively controlling the piezoelectric elements, it is shown that the periodic rods can efficiently attenuate the propagation of vibration from the upper plate to the lower one within critical frequency bands and consequently minimize the effects of transmission of undesirable vibration and sound radiation. In such a system, longitudinal waves can propagate from the vibration source in the upper plate to the lower one along the rods only within specific frequency bands called the "Pass Bands" and wave propagation is efficiently attenuated within other frequency bands called the "Stop Bands". The spectral width of these bands can be tuned according to the nature of the external excitation. The theory governing the operation of this class of vibration isolator is presented and their tunable filtering characteristics are demonstrated experimentally as functions of their design parameters. This concept can be employed in many applications to control the wave propagation and the force transmission of longitudinal vibrations both in the spectral and spatial domains in an attempt to stop/attenuate the propagation of undesirable disturbances.

  20. 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.

  1. Alveolar architecture of clear cell renal carcinomas (≤5.0 cm) show high attenuation on dynamic CT scanning

    International Nuclear Information System (INIS)

    Fujimoto, Hiroyuki; Wakao, Fumihiko; Moriyama, Noriyuki; Tobisu, Kenichi; Kakizoe, Tadao; Sakamoto, Michiie

    1999-01-01

    To establish the correlation between tumor appearance on CT and tumor histology in renal cell carcinomas. The density and attenuation patterns of 96 renal cell carcinomas, each ≤5 cm in greatest diameter, were studied by non-enhanced CT and early and late after bolus injection of contrast medium using dynamic CT. The density and attenuation patterns and pathological maps of each tumor were individually correlated. High attenuated areas were present in 72 of the 96 tumors on early enhanced dynamic CT scanning. All 72 high attenuated areas were of the clear cell renal cell carcinoma and had alveolar architecture. The remaining 24 tumors that did not demonstrate high attenuated foci on early enhanced scanning included three clear cell, nine granular cell, six papillary, five chromophobe and one collecting duct type. With respect to tumor architecture, all clear cell tumors of alveolar architecture demonstrated high attenuation on early enhanced scanning. Clear cell renal cell carcinomas of alveolar architecture show high attenuation on early enhanced dynamic CT scanning. A larger number of patients are indispensable to obtaining clear results. However, these findings seem to be an important clue to the diagnosis of renal cell carcinomas as having an alveolar structure. (author)

  2. Optimization of attenuation estimation in reflection for in vivo human dermis characterization at 20 MHz.

    Science.gov (United States)

    Fournier, Céline; Bridal, S Lori; Coron, Alain; Laugier, Pascal

    2003-04-01

    In vivo skin attenuation estimators must be applicable to backscattered radio frequency signals obtained in a pulse-echo configuration. This work compares three such estimators: short-time Fourier multinarrowband (MNB), short-time Fourier centroid shift (FC), and autoregressive centroid shift (ARC). All provide estimations of the attenuation slope (beta, dB x cm(-1) x MHz(-1)); MNB also provides an independent estimation of the mean attenuation level (IA, dB x cm(-1)). Practical approaches are proposed for data windowing, spectral variance characterization, and bandwidth selection. Then, based on simulated data, FC and ARC were selected as the best (compromise between bias and variance) attenuation slope estimators. The FC, ARC, and MNB were applied to in vivo human skin data acquired at 20 MHz to estimate betaFC, betaARC, and IA(MNB), respectively (without diffraction correction, between 11 and 27 MHz). Lateral heterogeneity had less effect and day-to-day reproducibility was smaller for IA than for beta. The IA and betaARC were dependent on pressure applied to skin during acquisition and IA on room and skin-surface temperatures. Negative values of IA imply that IA and beta may be influenced not only by skin's attenuation but also by structural heterogeneity across dermal depth. Even so, IA was correlated to subject age and IA, betaFC, and betaARC were dependent on subject gender. Thus, in vivo attenuation measurements reveal interesting variations with subject age and gender and thus appeared promising to detect skin structure modifications.

  3. 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

    highest for cortCT (40.8%, range: 1.5% to 110.8%). For soft tissue lesions the bias was highest using cortCT (13.4%, range: –2.3% to 17.3%) and lowest for spongCT (–2.2%, range: 0.0% to –13.7%). Conclusions: In PET/MR imaging using standard MR-AC PET uptake values in soft lesions and bone lesions are underestimated by about 10%. In individual patients this bias can be as high as 22%, which is significant during clinical follow-up exams. If bone segmentation is available, then assigning a fixed attenuation value of spongious bone to all bone structures appears reasonable and results in only a minor bias of 5%, or less in uptake values of soft tissue and bone lesions.

  4. Identification of sequence changes in live attenuated goose parvovirus vaccine strains developed in Asia and Europe.

    Science.gov (United States)

    Shien, J-H; Wang, Y-S; Chen, C-H; Shieh, H K; Hu, C-C; Chang, P-C

    2008-10-01

    Live attenuated vaccines have been used for control of the disease caused by goose parvovirus (GPV), but the mechanism involved in attenuation of GPV remains elusive. This report presents the complete nucleotide sequences of two live attenuated strains of GPV (82-0321V and VG32/1) that were independently developed in Taiwan and Europe, together with the parental strain of 82-0321V and a field strain isolated in Taiwan in 2006. Sequence comparisons showed that 82-0321V and VG32/1 had multiple deletions and substitutions in the inverted terminal repeats region when compared with their parental strain or the field virus, but these changes did not affect the formation of the hairpin structure essential for viral replication. Moreover, 82-0321V and VG32/1 had five amino acid changes in the non-structural protein, but these changes were located at positions distant from known functional motifs in the non-structural protein. In contrast, 82-0321V had nine changes and VG32/1 had 11 changes in their capsid proteins (VP1), and the majority of these changes occurred at positions close to the putative receptor binding sites of VP1, as predicted using the structure of adeno-associated virus 2 as the model system. Taken together, the results suggest that changes in sequence near the receptor binding sites of VP1 might be responsible for attenuation of GPV. This is the first report of complete nucleotide sequences of GPV other than the virulent B strain, and suggests a possible mechanism for attenuation of GPV.

  5. Uranium soft x-ray total attenuation coefficients

    International Nuclear Information System (INIS)

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

    1981-01-01

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

  6. Seismic random noise attenuation using shearlet and total generalized variation

    International Nuclear Information System (INIS)

    Kong, Dehui; Peng, Zhenming

    2015-01-01

    Seismic denoising from a corrupted observation is an important part of seismic data processing which improves the signal-to-noise ratio (SNR) and resolution. In this paper, we present an effective denoising method to attenuate seismic random noise. The method takes advantage of shearlet and total generalized variation (TGV) regularization. Different regularity levels of TGV improve the quality of the final result by suppressing Gibbs artifacts caused by the shearlet. The problem is formulated as mixed constraints in a convex optimization. A Bregman algorithm is proposed to solve the proposed model. Extensive experiments based on one synthetic datum and two post-stack field data are done to compare performance. The results demonstrate that the proposed method provides superior effectiveness and preserve the structure better. (paper)

  7. Using ultrasonic attenuation for assessing the fatigue damage of concrete

    International Nuclear Information System (INIS)

    Suaris, W.; Fernando, V.

    1987-01-01

    The results from cyclic loading tests indicate that damage accumulation as measured by pulse attenuation during cyclic loading is not linear, particularly during the initial cycles. The crack growth results obtained may be used for ascertaining the extent of damage in a in-situ structure using the following procedure: The ultrasonic waveforms obtained from a damaged region can first be compared with that obtained from the same region initially to yield a damage coefficient. Then the calibration charts obtained from laboratory specimens may be used to predict the extent of damage due to cyclic loading. The proposed method can also easily be extended to predict the deterioration due to shrinkage, creep and other environmental effects as long as their effect is to produce cracking in the concrete. (orig./HP)

  8. Seismic random noise attenuation using shearlet and total generalized variation

    Science.gov (United States)

    Kong, Dehui; Peng, Zhenming

    2015-12-01

    Seismic denoising from a corrupted observation is an important part of seismic data processing which improves the signal-to-noise ratio (SNR) and resolution. In this paper, we present an effective denoising method to attenuate seismic random noise. The method takes advantage of shearlet and total generalized variation (TGV) regularization. Different regularity levels of TGV improve the quality of the final result by suppressing Gibbs artifacts caused by the shearlet. The problem is formulated as mixed constraints in a convex optimization. A Bregman algorithm is proposed to solve the proposed model. Extensive experiments based on one synthetic datum and two post-stack field data are done to compare performance. The results demonstrate that the proposed method provides superior effectiveness and preserve the structure better.

  9. Gamma ray attenuation studies on concrete reinforced with coconut shells

    International Nuclear Information System (INIS)

    Vishnu, C.V.; Antony, Joseph

    2017-01-01

    The fact that radiation could be harmful has led to the development of wide variety of shields to protect against it. For nuclear radiation shielding, a larger quantity of shielding material is required and therefore, the study of propagation of radiation flux in shielding materials is an essential requirement for shield design. Concrete has proven to be an excellent and versatile shielding material with well-established linear attenuation for neutrons and gamma rays. Coconut being naturally available, it can be used readily in concrete, still maintaining almost all the qualities of the original form of concrete. Concrete obtained using coconut shell as a coarse aggregate satisfies the requirements of concrete. Coconut shell aggregate possess acceptable strength which is required for structural concrete

  10. Large photonic band gaps and strong attenuations of two-segment-connected Peano derivative networks

    International Nuclear Information System (INIS)

    Lu, Jian; Yang, Xiangbo; Zhang, Guogang; Cai, Lianzhang

    2011-01-01

    In this Letter, based on ancient Peano curves we construct four kinds of interesting Peano derivative networks composed of one-dimensional (1D) waveguides and investigate the optical transmission spectra and photonic attenuation behavior of electromagnetic (EM) waves in one- and two-segment-connected networks. It is found that for some two-segment-connected networks large photonic band gaps (PBGs) can be created and the widths of large PBGs can be controlled by adjusting the matching ratio of waveguide length and are insensitive to generation number. Diamond- and hexagon-Peano networks are good selectable structures for the designing of optical devices with large PBG(s) and strong attenuation(s). -- Highlights: → Peano and Peano derivative networks composed of 1D waveguides are designed. → Large PBGs with strong attenuations have been created by these fractal networks. → New approach for designing optical devices with large PBGs is proposed. → Diamond- and hexagon-Peano networks with d2:d1=2:1 are good selectable structures.

  11. Scatter and attenuation correction in SPECT

    International Nuclear Information System (INIS)

    Ljungberg, Michael

    2004-01-01

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

  12. Attenuation correction using simultaneous emission - transmission tomography

    International Nuclear Information System (INIS)

    Ljubenov, V.; Marinkovic, P.

    1998-01-01

    In order to reduce degrading influence of attenuation on SPECT image quality, possibility for correction, based on simultaneous emission / transmission measurements, is discussed. Numerical photon transport simulations through the phantom and acquisition of of tomographic projections are performed by using Monte Carlo code MCNP-4A. Amount of contamination in transmission data due to photon Compton scattering for emission energy window is specially analyzed and appropriate spatial depending 'noise / signal' factors for three different external sources, applied with Tc-99m, are determined (author)

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

    International Nuclear Information System (INIS)

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

    2015-01-01

    Seismic attenuation in fluid-saturated porous rocks can occur by geometric spreading, wave scattering or the internal dissipation of energy, most likely due to the squirt-flow mechanism. In principle, the pattern of seismic attenuation recorded on an array of sensors contains information about the medium, in terms of material heterogeneity and anisotropy, as well as material properties such as porosity, crack density, and pore-fluid composition and mobility. In practice, this inverse problem is challenging. Here we provide some insights into the effects of internal dissipation by analysing synthetic data produced by a hybrid numerical and analytical model for seismic wave propagation in a fractured medium embedded within a layered geological structure. The model is made up of one anisotropic and three isotropic horizontal layers. The anisotropic layer consists of a porous, fluid-saturated material containing vertically aligned inclusions representing a set of fractures. This combination allows squirt-flow to occur between the pores in the matrix and the model fractures. Our results show that the fluid mobility and the associated relaxation time of the fluid-pressure gradient control the frequency range over which attenuation occurs. This induced attenuation increases with incidence angle and azimuth away from the fracture strike-direction. Azimuthal variations in the induced attenuation are elliptical allowing the fracture orientations to be obtained from the axes of the ellipse. These observations hold out the potential of using seismic attenuation as an additional diagnostic in the characterisation of rock formations for a variety of applications including hydrocarbon exploration and production, subsurface storage of CO 2 , and geothermal energy extraction. (paper)

  14. Quantitative Evaluation of Segmentation- and Atlas-Based Attenuation Correction for PET/MR on Pediatric Patients.

    Science.gov (United States)

    Bezrukov, Ilja; Schmidt, Holger; Gatidis, Sergios; Mantlik, Frédéric; Schäfer, Jürgen F; Schwenzer, Nina; Pichler, Bernd J

    2015-07-01

    Pediatric imaging is regarded as a key application for combined PET/MR imaging systems. Because existing MR-based attenuation-correction methods were not designed specifically for pediatric patients, we assessed the impact of 2 potentially influential factors: inter- and intrapatient variability of attenuation coefficients and anatomic variability. Furthermore, we evaluated the quantification accuracy of 3 methods for MR-based attenuation correction without (SEGbase) and with bone prediction using an adult and a pediatric atlas (SEGwBONEad and SEGwBONEpe, respectively) on PET data of pediatric patients. The variability of attenuation coefficients between and within pediatric (5-17 y, n = 17) and adult (27-66 y, n = 16) patient collectives was assessed on volumes of interest (VOIs) in CT datasets for different tissue types. Anatomic variability was assessed on SEGwBONEad/pe attenuation maps by computing mean differences to CT-based attenuation maps for regions of bone tissue, lungs, and soft tissue. PET quantification was evaluated on VOIs with physiologic uptake and on 80% isocontour VOIs with elevated uptake in the thorax and abdomen/pelvis. Inter- and intrapatient variability of the bias was assessed for each VOI group and method. Statistically significant differences in mean VOI Hounsfield unit values and linear attenuation coefficients between adult and pediatric collectives were found in the lungs and femur. The prediction of attenuation maps using the pediatric atlas showed a reduced error in bone tissue and better delineation of bone structure. Evaluation of PET quantification accuracy showed statistically significant mean errors in mean standardized uptake values of -14% ± 5% and -23% ± 6% in bone marrow and femur-adjacent VOIs with physiologic uptake for SEGbase, which could be reduced to 0% ± 4% and -1% ± 5% using SEGwBONEpe attenuation maps. Bias in soft-tissue VOIs was less than 5% for all methods. Lung VOIs showed high SDs in the range of 15% for

  15. Attenuation of pressure dips underneath piles of spherocylinders.

    Science.gov (United States)

    Zhao, Haiyang; An, Xizhong; Gou, Dazhao; Zhao, Bo; Yang, Runyu

    2018-05-30

    The discrete element method (DEM) was used to simulate the piling of rod-like (elongated sphero-cylindrical) particles, mainly focusing on the effect of particle shape on the structural and force properties of the piles. In this work, rod-like particles of different aspect ratios were discharged on a flat surface to form wedge-shaped piles. The surface properties of the piles were characterized in terms of angle of repose and stress at the bottom of the piles. The results showed that the rise of the angle of repose became slower with the increase of particle aspect ratio. The pressure dip underneath the piles reached the maximum when the particle aspect ratio was around 1.6, beyond which the pressure dip phenomenon became attenuated. Both the pressure dip and the shear stress dip were quantitatively examined. The structure and forces inside the piles were further analyzed to understand the change in pressure dip, indicating that "bridging" or "arching" structures within the piles were the cause of the pressure dip.

  16. Attenuation of postoperative adhesions using a modeled manual therapy.

    Directory of Open Access Journals (Sweden)

    Geoffrey M Bove

    Full Text Available Postoperative adhesions are pathological attachments that develop between abdominopelvic structures following surgery. Considered unavoidable and ubiquitous, postoperative adhesions lead to bowel obstructions, infertility, pain, and reoperations. As such, they represent a substantial health care challenge. Despite over a century of research, no preventive treatment exists. We hypothesized that postoperative adhesions develop from a lack of movement of the abdominopelvic organs in the immediate postoperative period while rendered immobile by surgery and opiates, and tested whether manual therapy would prevent their development. In a modified rat cecal abrasion model, rats were allocated to receive treatment with manual therapy or not, and their resulting adhesions were quantified. We also characterized macrophage phenotype. In separate experiments we tested the safety of the treatment on a strictureplasty model, and also the efficacy of the treatment following adhesiolysis. We show that the treatment led to reduced frequency and size of cohesive adhesions, but not other types of adhesions, such as those involving intraperitoneal fatty structures. This effect was associated with a delay in the appearance of trophic macrophages. The treatment did not inhibit healing or induce undesirable complications following strictureplasty. Our results support that that maintained movements of damaged structures in the immediate postoperative period has potential to act as an effective preventive for attenuating cohesive postoperative adhesion development. Our findings lay the groundwork for further research, including mechanical and pharmacologic approaches to maintain movements during healing.

  17. Attenuation of postoperative adhesions using a modeled manual therapy.

    Science.gov (United States)

    Bove, Geoffrey M; Chapelle, Susan L; Hanlon, Katherine E; Diamond, Michael P; Mokler, David J

    2017-01-01

    Postoperative adhesions are pathological attachments that develop between abdominopelvic structures following surgery. Considered unavoidable and ubiquitous, postoperative adhesions lead to bowel obstructions, infertility, pain, and reoperations. As such, they represent a substantial health care challenge. Despite over a century of research, no preventive treatment exists. We hypothesized that postoperative adhesions develop from a lack of movement of the abdominopelvic organs in the immediate postoperative period while rendered immobile by surgery and opiates, and tested whether manual therapy would prevent their development. In a modified rat cecal abrasion model, rats were allocated to receive treatment with manual therapy or not, and their resulting adhesions were quantified. We also characterized macrophage phenotype. In separate experiments we tested the safety of the treatment on a strictureplasty model, and also the efficacy of the treatment following adhesiolysis. We show that the treatment led to reduced frequency and size of cohesive adhesions, but not other types of adhesions, such as those involving intraperitoneal fatty structures. This effect was associated with a delay in the appearance of trophic macrophages. The treatment did not inhibit healing or induce undesirable complications following strictureplasty. Our results support that that maintained movements of damaged structures in the immediate postoperative period has potential to act as an effective preventive for attenuating cohesive postoperative adhesion development. Our findings lay the groundwork for further research, including mechanical and pharmacologic approaches to maintain movements during healing.

  18. Vinpocetine attenuates lipid accumulation and atherosclerosis formation

    International Nuclear Information System (INIS)

    Cai, Yujun; Li, Jian-Dong; Yan, Chen

    2013-01-01

    Highlights: •Vinpocetine attenuates hyperlipidemia-induced atherosclerosis in a mouse model. •Vinpocetine antagonizes ox-LDL uptake and accumulation in macrophages. •Vinpocetine blocks the induction of ox-LDL receptor LOX-1 in vitro and in vivo. -- Abstract: Atherosclerosis, the major cause of myocardial infarction and stroke, is a chronic arterial disease characterized by lipid deposition and inflammation in the vessel wall. Cholesterol, in low-density lipoprotein (LDL), plays a critical role in the pathogenesis of atherosclerosis. Vinpocetine, a derivative of the alkaloid vincamine, has long been used as a cerebral blood flow enhancer for treating cognitive impairment. Recent study indicated that vinpocetine is a potent anti-inflammatory agent. However, its role in the pathogenesis of atherosclerosis remains unexplored. In the present study, we show that vinpocetine significantly reduced atherosclerotic lesion formation in ApoE knockout mice fed with a high-fat diet. In cultured murine macrophage RAW264.7 cells, vinpocetine markedly attenuated oxidized LDL (ox-LDL) uptake and foam cell formation. Moreover, vinpocetine greatly blocked the induction of ox-LDL receptor 1 (LOX-1) in cultured macrophages as well as in the LOX-1 level in atherosclerotic lesions. Taken together, our data reveal a novel role of vinpocetine in reduction of pathogenesis of atherosclerosis, at least partially through suppressing LOX-1 signaling pathway. Given the excellent safety profile of vinpocetine, this study suggests vinpocetine may be a therapeutic candidate for treating atherosclerosis

  19. Ultra-low acoustoelectric attenuation in graphene

    Science.gov (United States)

    Tang, Chiu-Chun; Chen, Yung-Fu; Ling, D. C.; Chi, C. C.; Chen, Jeng-Chung

    2017-03-01

    We investigate the acoustoelectric properties of graphene and extract its acoustoelectric attenuation Γ as a function of the carrier density n, tuned via ionic liquid gating. Acoustoelectric effects in graphene are induced by launching surface acoustic waves (SAWs) on a piezoelectric LiNbO3 substrate. We measure the acoustoelectric current Iae through graphene and extract the SAW attenuation factor Γ as a function of n. The magnitude of Iae increases with decreasing n when the n is far from the charge neutral point (CNP). When n is tuned across the CNP, Iae first exhibits a local maximum, vanishes at the CNP, and then changes sign in accordance with the associated change in the carrier polarity. By contrast, Γ monotonically increases with decreasing n and reaches a maximum at the CNP. The extracted values of Γ, calibrated at the central frequency of 189 MHz, vary from ˜0.4 m-1 to 6.8 m-1, much smaller than the values for known two-dimensional systems. Data analysis suggests that the evolution of Iae and Γ with n manifests the electronic states of graphene. Our experimental findings provide insightful information for developing innovative graphene-based devices.

  20. Cranking model and attenuation of Coriolis interaction

    International Nuclear Information System (INIS)

    Lyutorovich, N.A.

    1987-01-01

    Description of rotational bands of odd deformed nuclei in the self-consistent Cranking model (SCM) is given. Causes of attenuation of the Coriolis interaction in the nuclei investigated are studied, and account of bound of one-particle degrees of freedom with rotation of the Hartree-Fock-Bogolyubov (HFB) self-consistent method is introduced additionally to SCM for qualitative agreement with experimental data. Merits and shortages of SCM in comparison with the quadruparticle-rotor (QR) model are discussed. All know ways for constructing the Hamiltonian QR model (or analog of such Hamiltonian) on the basis of the microscopic theory are shown to include two more approximations besides others: quasi-particle-rotational interaction leading to pair break is taken into account in the second order of the perturbation theory; some exchange diagrams are neglected among diagrams of the second order according to this interaction. If one makes the same approximations in SCM instead of HFB method, then the dependence of level energies on spin obtained in this case is turned out to be close to the results of the QR model. Besides, the problem on renormalization of matrix elements of quasi-rotational interaction occurs in such nonself-consistent approach as in the QR model. In so far as the similar problem does not occur in SCM, one can make the conclusion that the problem of attenuation of Coriolis interaction involves the approximations given above

  1. Electron attenuation in free, neutral ethane clusters.

    Science.gov (United States)

    Winkler, M; Myrseth, V; Harnes, J; Børve, K J

    2014-10-28

    The electron effective attenuation length (EAL) in free, neutral ethane clusters has been determined at 40 eV kinetic energy by combining carbon 1s x-ray photoelectron spectroscopy and theoretical lineshape modeling. More specifically, theory is employed to form model spectra on a grid in cluster size (N) and EAL (λ), allowing N and λ to be determined by optimizing the goodness-of-fit χ(2)(N, λ) between model and observed spectra. Experimentally, the clusters were produced in an adiabatic-expansion setup using helium as the driving gas, spanning a range of 100-600 molecules in mean cluster size. The effective attenuation length was determined to be 8.4 ± 1.9 Å, in good agreement with an independent estimate of 10 Å formed on the basis of molecular electron-scattering data and Monte Carlo simulations. The aggregation state of the clusters as well as the cluster temperature and its importance to the derived EAL value are discussed in some depth.

  2. Vinpocetine attenuates lipid accumulation and atherosclerosis formation

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Yujun [Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester, 601 Elmwood Ave, Rochester, NY 14642 (United States); Li, Jian-Dong [Center for Inflammation, Immunity and Infection, and Department of Biology, Georgia State University, Atlanta, GA 30303 (United States); Yan, Chen, E-mail: Chen_Yan@urmc.rochester.edu [Aab Cardiovascular Research Institute, Department of Medicine, University of Rochester, 601 Elmwood Ave, Rochester, NY 14642 (United States)

    2013-05-10

    Highlights: •Vinpocetine attenuates hyperlipidemia-induced atherosclerosis in a mouse model. •Vinpocetine antagonizes ox-LDL uptake and accumulation in macrophages. •Vinpocetine blocks the induction of ox-LDL receptor LOX-1 in vitro and in vivo. -- Abstract: Atherosclerosis, the major cause of myocardial infarction and stroke, is a chronic arterial disease characterized by lipid deposition and inflammation in the vessel wall. Cholesterol, in low-density lipoprotein (LDL), plays a critical role in the pathogenesis of atherosclerosis. Vinpocetine, a derivative of the alkaloid vincamine, has long been used as a cerebral blood flow enhancer for treating cognitive impairment. Recent study indicated that vinpocetine is a potent anti-inflammatory agent. However, its role in the pathogenesis of atherosclerosis remains unexplored. In the present study, we show that vinpocetine significantly reduced atherosclerotic lesion formation in ApoE knockout mice fed with a high-fat diet. In cultured murine macrophage RAW264.7 cells, vinpocetine markedly attenuated oxidized LDL (ox-LDL) uptake and foam cell formation. Moreover, vinpocetine greatly blocked the induction of ox-LDL receptor 1 (LOX-1) in cultured macrophages as well as in the LOX-1 level in atherosclerotic lesions. Taken together, our data reveal a novel role of vinpocetine in reduction of pathogenesis of atherosclerosis, at least partially through suppressing LOX-1 signaling pathway. Given the excellent safety profile of vinpocetine, this study suggests vinpocetine may be a therapeutic candidate for treating atherosclerosis.

  3. Engineering a Light-Attenuating Artificial Iris.

    Science.gov (United States)

    Shareef, Farah J; Sun, Shan; Kotecha, Mrignayani; Kassem, Iris; Azar, Dimitri; Cho, Michael

    2016-04-01

    Discomfort from light exposure leads to photophobia, glare, and poor vision in patients with congenital or trauma-induced iris damage. Commercial artificial iris lenses are static in nature to provide aesthetics without restoring the natural iris's dynamic response to light. A new photo-responsive artificial iris was therefore developed using a photochromic material with self-adaptive light transmission properties and encased in a transparent biocompatible polymer matrix. The implantable artificial iris was designed and engineered using Photopia, a class of photo-responsive materials (termed naphthopyrans) embedded in polyethylene. Photopia was reshaped into annular disks that were spin-coated with polydimethylsiloxane (PDMS) to form our artificial iris lens of controlled thickness. Activated by UV and blue light in approximately 5 seconds with complete reversal in less than 1 minute, the artificial iris demonstrates graded attenuation of up to 40% of visible and 60% of UV light. There optical characteristics are suitable to reversibly regulate the incident light intensity. In vitro cell culture experiments showed up to 60% cell death within 10 days of exposure to Photopia, but no significant cell death observed when cultured with the artificial iris with protective encapsulation. Nuclear magnetic resonance spectroscopy confirmed these results as there was no apparent leakage of potentially toxic photochromic material from the ophthalmic device. Our artificial iris lens mimics the functionality of the natural iris by attenuating light intensity entering the eye with its rapid reversible change in opacity and thus potentially providing an improved treatment option for patients with iris damage.

  4. 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

  5. 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.

  6. 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.

  7. 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

  8. 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

  9. An attenuated projector-backprojector for iterative SPECT reconstruction

    International Nuclear Information System (INIS)

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

    1985-01-01

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

  10. 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)

  11. Attenuation tomography in the rupture area of the 2010 M8.8 Maule, Chile, earthquake

    Science.gov (United States)

    Heather-Smith, Helen; Rietbrock, Andreas

    2016-04-01

    In recent years several seismological studies have developed a detailed image of the megathrust interface between the subducting Nazca plate and and the overriding South American plate in the rupture area of the 2010 M8.8 Maule, Chile, earthquake. Hicks et al. (2014) have published a high resolution 3D seismic tomography model and characterised the different regimes acting along the interface based on their seismic properties. A more detailed study by Moreno et al. (2014) showed that the seismic Vp/Vs ratio and inter-seismic locking determined from GPS measurements are correlated. Together these observations open up the possibility to map the rupture potential of possible future earthquakes, although the underlying processes are yet not fully understood and a more in depth analysis of other physical properties is needed. 3D seismic attenuation structure as well as seismic stress-drop distribution based on the aftershock seismicity are providing independent data sets to better constrain the physical processes acting along the subduction zone interface. As seismic attenuation is particularly sensitive to fluid saturation it opens up the possibility to study more directly the influence of fluids on aftershock activity as compared to standard velocity tomography studies. Based on our event catalogue of approximately 30,000 aftershocks we are currently selecting the most appropriate data set for the staggered 3D attenuation tomography. The inverted attenuation model will then be used to calculate seismic stress drop values for the complete aftershock catalogue. We will present our preliminary 3D attenuation model together with our stress drop estimates and compare our finding to the 3D velocity structure and slip distribution.

  12. 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)

  13. 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

  14. 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.

  15. 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.

  16. Attenuation of multiples in image space

    Science.gov (United States)

    Alvarez, Gabriel F.

    In complex subsurface areas, attenuation of 3D specular and diffracted multiples in data space is difficult and inaccurate. In those areas, image space is an attractive alternative. There are several reasons: (1) migration increases the signal-to-noise ratio of the data; (2) primaries are mapped to coherent events in Subsurface Offset Domain Common Image Gathers (SODCIGs) or Angle Domain Common Image Gathers (ADCIGs); (3) image space is regular and smaller; (4) attenuating the multiples in data space leaves holes in the frequency-Wavenumber space that generate artifacts after migration. I develop a new equation for the residual moveout of specular multiples in ADCIGs and use it for the kernel of an apex-shifted Radon transform to focus and separate the primaries from specular and diffracted multiples. Because of small amplitude, phase and kinematic errors in the multiple estimate, we need adaptive matching and subtraction to estimate the primaries. I pose this problem as an iterative least-squares inversion that simultaneously matches the estimates of primaries and multiples to the data. Standard methods match only the estimate of the multiples. I demonstrate with real and synthetic data that the method produces primaries and multiples with little cross-talk. In 3D, the multiples exhibit residual moveout in SODCIGs in in-line and cross-line offsets. They map away from zero subsurface offsets when migrated with the faster velocity of the primaries. In ADCIGs the residual moveout of the primaries as a function of the aperture angle, for a given azimuth, is flat for those angles that illuminate the reflector. The multiples have residual moveout towards increasing depth for increasing aperture angles at all azimuths. As a function of azimuth, the primaries have better azimuth resolution than the multiples at larger aperture angles. I show, with a real 3D dataset, that even below salt, where illumination is poor, the multiples are well attenuated in ADCIGs with the new

  17. Vibration Attenuation by a Combination of a Piezoelectric Stack and a Permanent Magnet

    Directory of Open Access Journals (Sweden)

    A. Nandi

    2012-01-01

    Full Text Available The present work proposes a non-contact vibration attenuator made up of a permanent magnet mounted on a piezoelectric stack. Two such actuators are made to work simultaneously in a 'twin-actuator' configuration. It is conceived that a controlled change in the gap between the actuator and the structure is capable of attenuation of vibration of the structure. This appropriate change in gap is achieved by controlled motion of the piezoelectric stacks. It is shown that the actuator works as an active damper when the extension and contraction of the actuators are made proportional to the velocity of the beam. The resolution of extension of a piezoelectric stack is in the order of nanometers. Thus in the proposed actuator the force of actuation can be applied with great precision. This actuator is also attractive for its simple constructional feature.

  18. Critical coupling of surface plasmons in graphene attenuated total reflection geometry

    Energy Technology Data Exchange (ETDEWEB)

    Cuevas, Mauro, E-mail: cuevas@df.uba.ar [Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Facultad de Ingeniería y Tecnología Informática, Universidad de Belgrano, Villanueva 1324, C1426BMJ, Buenos Aires (Argentina); Grupo de Electromagnetismo Aplicado, Departamento de Física, FCEN, Universidad de Buenos Aires and IFIBA, Ciudad Universitaria, Pabellón I, C1428EHA, Buenos Aires (Argentina)

    2016-12-09

    We study the optical response of an attenuated total reflection (ATR) structure in Otto configuration with graphene sheet, paying especial attention to the occurrence of total absorption. Our results show that due to excitation of surface plasmons on the graphene sheet, two different conditions of total absorption may occur. At these conditions, the energy loss of the surface plasmon by radiation is equal to its energy loss by absorption into the graphene sheet. We give necessary conditions on ATR parameters for the existence of total absorption. - Highlights: • Attenuated total reflection (ATR) structure with graphene sheet. • Surface plasmons and power matched condition. • Necessary conditions on ATR parameters for the existence of total absorption.

  19. Critical coupling of surface plasmons in graphene attenuated total reflection geometry

    International Nuclear Information System (INIS)

    Cuevas, Mauro

    2016-01-01

    We study the optical response of an attenuated total reflection (ATR) structure in Otto configuration with graphene sheet, paying especial attention to the occurrence of total absorption. Our results show that due to excitation of surface plasmons on the graphene sheet, two different conditions of total absorption may occur. At these conditions, the energy loss of the surface plasmon by radiation is equal to its energy loss by absorption into the graphene sheet. We give necessary conditions on ATR parameters for the existence of total absorption. - Highlights: • Attenuated total reflection (ATR) structure with graphene sheet. • Surface plasmons and power matched condition. • Necessary conditions on ATR parameters for the existence of total absorption.

  20. Attenuation and Dispersion in Earth's Materials

    Science.gov (United States)

    Gueguen, Y.

    2012-04-01

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

  1. Glutathione attenuates uranyl toxicity in Lactococcus lactis

    Energy Technology Data Exchange (ETDEWEB)

    Fahmy, Karim; Oertel, Jana [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Biophysics; Obeid, M. [Technische Univ. Dresden (Germany); Solioz, M. [Bern Univ. (Switzerland)

    2017-06-01

    We investigated the role of intracellular glutathione (GSH), which in a large number of taxa plays a role in the protection against the toxicity of heavy metals. Anaerobically grown Lactococcus lactis containing an inducible GSH synthesis pathway was used as a model organism allowing the study of GSH-dependent uranyl detoxification without interference from additional reactive oxygen species. Microcalorimetric measurements of the metabolic heat showed that intracellular GSH attenuates the toxicity of uranium at a concentration in the range of 10-150 μM. Isothermal titration calorimetry revealed the endothermic binding of U(VI) to the carboxyl group(s) of GSH. The data indicate that the primary detoxifying mechanism is the intracellular sequestration of carboxyl-coordinated U(VI) into an insoluble complex with GSH.

  2. Factors influencing radon attenuation by tailing covers

    International Nuclear Information System (INIS)

    Silker, W.B.; Rogers, V.C.

    1981-07-01

    The US NRC, in its Generic Environmental Impact Statement on uranium milling has specified that the radon flux escaping a uranium mill tailings pile will be reduced to pCi/m 2 s by application of covering layers of soils and clays. These covers present a radon diffusion barrier, which sufficiently increases the time required for radon passage from the tailings to the atmosphere to allow for decay of 222 Rn within the cover. The depth of cover necessary to reduce the escaping radon flux to the prescribed level is to be determined by calculation, and requires precise knowledge of the radon diffusion coefficient in the covering media. A Radon Attenuation Test Facility was developed to determine rates of radon diffusion through candidate cover materials. This paper describes this facility and its application for determining the influence of physical properties of the soil column on the radon diffusion coefficient

  3. Glutathione attenuates uranyl toxicity in Lactococcus lactis

    International Nuclear Information System (INIS)

    Fahmy, Karim; Oertel, Jana; Solioz, M.

    2017-01-01

    We investigated the role of intracellular glutathione (GSH), which in a large number of taxa plays a role in the protection against the toxicity of heavy metals. Anaerobically grown Lactococcus lactis containing an inducible GSH synthesis pathway was used as a model organism allowing the study of GSH-dependent uranyl detoxification without interference from additional reactive oxygen species. Microcalorimetric measurements of the metabolic heat showed that intracellular GSH attenuates the toxicity of uranium at a concentration in the range of 10-150 μM. Isothermal titration calorimetry revealed the endothermic binding of U(VI) to the carboxyl group(s) of GSH. The data indicate that the primary detoxifying mechanism is the intracellular sequestration of carboxyl-coordinated U(VI) into an insoluble complex with GSH.

  4. Release and attenuation of fluorocarbons in landfills

    DEFF Research Database (Denmark)

    Kjeldsen, Peter; Scheutz, Charlotte

    2003-01-01

    Several halocarbons with very high global warming and ozone depleting potentials have been used as blowing agent for insulation foam in refrigerators and freezers. Many appliances are shredded after the end of their useful life. Release experiments carried out in the laboratory on insulation foam...... blown with CFC-11, HCFC-141b, HFC- 134a, and HFC-245fa revealed that most of the blowing agent is not released to the atmosphere during a six-week period following the shredding process. The fraction which is released in the six-week period is highly dependent on how fine the foam is shredded....... The residual blowing agent remaining after the six-week period may be very slowly released if the integrity of the foam particles with respect to diffusional properties is kept after disposal of the foam waste in landfills. Laboratory experiments simulating attenuation processes in the landfilled waste...

  5. Core disgust is attenuated by ingroup relations.

    Science.gov (United States)

    Reicher, Stephen D; Templeton, Anne; Neville, Fergus; Ferrari, Lucienne; Drury, John

    2016-03-08

    We present the first experimental evidence to our knowledge that ingroup relations attenuate core disgust and that this helps explain the ability of groups to coact. In study 1, 45 student participants smelled a sweaty t-shirt bearing the logo of another university, with either their student identity (ingroup condition), their specific university identity (outgroup condition), or their personal identity (interpersonal condition) made salient. Self-reported disgust was lower in the ingroup condition than in the other conditions, and disgust mediated the relationship between condition and willingness to interact with target. In study 2, 90 student participants smelled a sweaty target t-shirt bearing either the logo of their own university, another university, or no logo, with either their student identity or their specific university identity made salient. Walking time to wash hands and pumps of soap indicated that disgust was lower where the relationship between participant and target was ingroup rather than outgroup or ambivalent (no logo).

  6. Attenuation of species abundance distributions by sampling

    Science.gov (United States)

    Shimadzu, Hideyasu; Darnell, Ross

    2015-01-01

    Quantifying biodiversity aspects such as species presence/ absence, richness and abundance is an important challenge to answer scientific and resource management questions. In practice, biodiversity can only be assessed from biological material taken by surveys, a difficult task given limited time and resources. A type of random sampling, or often called sub-sampling, is a commonly used technique to reduce the amount of time and effort for investigating large quantities of biological samples. However, it is not immediately clear how (sub-)sampling affects the estimate of biodiversity aspects from a quantitative perspective. This paper specifies the effect of (sub-)sampling as attenuation of the species abundance distribution (SAD), and articulates how the sampling bias is induced to the SAD by random sampling. The framework presented also reveals some confusion in previous theoretical studies. PMID:26064626

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

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

    Science.gov (United States)

    Bezada, Maximiliano J.

    2017-11-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-05-15

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

  10. LIVE ATTENUATED VACCINES FOR THE IMMUNOPROPHYLAXIS

    Directory of Open Access Journals (Sweden)

    O. A. Shamsutdinova

    2017-01-01

    Full Text Available The review focuses on the history of the production of live antiviral vaccines and their use for the prevention of infectious diseases. It was noted that before the beginning of the 20th century, only three live vaccines were developed and put into practice — against smallpox, rabies, plague. The discovery of D. Enders, T.H. Weller and F.Ch. Robins of the ability of the polio virus, and then of a number of other viruses, to reproduce in vitro in cell cultures of various types, greatly expanded the studies on the production of attenuated strains of viruses for live vaccines. The historical stages of obtaining and introducing live vaccines for the prevention of smallpox, poliomyelitis, measles, rubella, and mumps are highlighted. Arguments in favor of the use of associated vaccine preparations for the prevention of viral infections are presented. Various variants of the strategy and tactics of using live vaccines, which are used for specific prevention of viral infections in different countries, are described. The review provides information on technological methods for obtaining antiviral vaccines. The publications testifying to the development of specific reactions in immunized vaccine strains of measles, mumps, poliomyelitis and rubella viruses, such as aseptic meningitis (vaccine strains of mumps virus, acute arthritis (vaccine rubella virus strains, temperature reactions, rash (vaccine strains of the virus Measles, vaccine-associated paralytic poliomyelitis (VAPP vaccine vaccine poliovirus. It is particularly noted that the long experience of vaccine prevention both in Russia and abroad convincingly shows that the risk of developing post-vaccination complications is incommensurably lower than the risk of causing harm to health from the corresponding infections. It is concluded that despite introduction of new third and fourth generation vaccines into practice, live attenuated vaccines do not lose their significance and are used in vaccine

  11. Engineering a Light-Attenuating Artificial Iris

    Science.gov (United States)

    Shareef, Farah J.; Sun, Shan; Kotecha, Mrignayani; Kassem, Iris; Azar, Dimitri; Cho, Michael

    2016-01-01

    Purpose Discomfort from light exposure leads to photophobia, glare, and poor vision in patients with congenital or trauma-induced iris damage. Commercial artificial iris lenses are static in nature to provide aesthetics without restoring the natural iris's dynamic response to light. A new photo-responsive artificial iris was therefore developed using a photochromic material with self-adaptive light transmission properties and encased in a transparent biocompatible polymer matrix. Methods The implantable artificial iris was designed and engineered using Photopia, a class of photo-responsive materials (termed naphthopyrans) embedded in polyethylene. Photopia was reshaped into annular disks that were spin-coated with polydimethylsiloxane (PDMS) to form our artificial iris lens of controlled thickness. Results Activated by UV and blue light in approximately 5 seconds with complete reversal in less than 1 minute, the artificial iris demonstrates graded attenuation of up to 40% of visible and 60% of UV light. There optical characteristics are suitable to reversibly regulate the incident light intensity. In vitro cell culture experiments showed up to 60% cell death within 10 days of exposure to Photopia, but no significant cell death observed when cultured with the artificial iris with protective encapsulation. Nuclear magnetic resonance spectroscopy confirmed these results as there was no apparent leakage of potentially toxic photochromic material from the ophthalmic device. Conclusions Our artificial iris lens mimics the functionality of the natural iris by attenuating light intensity entering the eye with its rapid reversible change in opacity and thus potentially providing an improved treatment option for patients with iris damage. PMID:27116547

  12. Attenuation Tomography Based on Strong Motion Data: Case Study of Central Honshu Region, Japan

    Science.gov (United States)

    Kumar, Parveen; Joshi, A.; Verma, O. P.

    2013-12-01

    Three-dimensional frequency dependent S-wave quality factor (Qβ(f)) value for the central Honshu region of Japan has been determined in this paper using an algorithm based on inversion of strong motion data. The method of inversion for determination of three-dimensional attenuation coefficients is proposed by H ashida and S himazaki (J Phys Earth. 32, 299-316, 1984) and has been used and modified by J oshi (Curr Sci. 90, 581-585, 2006; Nat Hazards. 43, 129-146, 2007) and J oshi et al. (J. Seismol. 14, 247-272, 2010). Twenty-one earthquakes digitally recorded on strong motion stations of Kik-net network have been used in this work. The magnitude of these earthquake ranges from 3.1 to 4.2 and depth ranging from 5 to 20 km, respectively. The borehole data having high signal to noise ratio and minimum site effect is used in the present work. The attenuation structure is determined by dividing the entire area into twenty-five three-dimensional blocks of uniform thickness having different frequency-dependent shear wave quality factor. Shear wave quality factor values have been determined at frequencies of 2.5, 7.0 and 10 Hz from record in a rectangular grid defined by 35.4°N to 36.4°N and 137.2°E to 138.2°E. The obtained attenuation structure is compared with the available geological features in the region and comparison shows that the obtained structure is capable of resolving important tectonic features present in the area. The proposed attenuation structure is compared with the probabilistic seismic hazard map of the region and shows that it bears some remarkable similarity in the patterns seen in seismic hazard map.

  13. Analysis of the JASPER Program Radial Shield Attenuation Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Slater, C.O.

    1993-01-01

    The results of the analysis of the JASPER Program Radial Shield Attenuation Experiment are presented. The experiment was performed in 1986 at the ORNL Tower Shielding Facility. It is the first of six experiments in this cooperative Japanese and American program in support of shielding designs for advanced sodium-cooled reactors. Six different shielding configurations and subconfigurations thereof were studied. The configurations were calculated with the DOT-IV two-dimensional discrete ordinates radiation transport computer code using the R-Z geometry option, a symmetric S{sub 12} quadrature (96 directions), and cross sections from ENDF/B versions IV and V in either a 51- or 61-group structure. Auxiliary codes were used to compute detector responses and prepare cross sections and source input for the DOT-IV calculations. Calculated detector responses were compared with measured responses and the agreement was good to excellent in many cases. However, the agreement for configurations having thick steel or B{sub 4}C regions or for some very large configurations was fair to poor. The disagreement was attributed to cross-section data, broad-group structure, or high background in the measurements. In particular, it is shown that two cross-section sets for ``B give very different results for neutron transmission through the thick B{sub 4}C regions used in one set of experimental configurations. Implications for design calculations are given.

  14. 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

  15. 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

  16. 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 ...

  17. 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

  18. 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)

  19. 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

  20. 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.

  1. Influence of density and mean atomic number on CT attenuation corrected PET: Phantom studies

    International Nuclear Information System (INIS)

    Maintas, D.; Houzard, C.; Galy, G.; Maintas, C.; Itti, R.; Cachin, F.; Mognetti, Th.; Slosman

    2007-01-01

    Aim: the aim of this work is to study the influence of medium density on the CT or external source attenuation corrected images, by simulation on a phantom, with various positron emission tomographs. Material and method: a series of experiments on a cylindrical phantom filled with water marked with [18 F]-FDG, containing six vials filled per pair with mediums of different densities or solutions of KI, CaCl 2 and saccharose with various densities, was carried out under comparable conditions on three different tomographs. In only one of the vials of each pair, an identical radioactivity of [18 F]-FDG was added, three to five fold the surrounding activity. The reconstructions and attenuation corrections suggested by the manufacturers, were carried out under the usual conditions of each site. The activity of each structure was estimated by the methods of profiles and regions of interest, on the non attenuation corrected images (N.A.C.), the images corrected by CT (C.T.A.C.), and/or external source (G.P.A.C.). Results: with all three tomographs, the activities estimated on the N.A.C. images present an inverse correlation to the medium density (important absorption by dense material). On C.T.A.C. images, we observed with only two of the three tomographs, an overestimation of the activity in the 'radioactive' vials, depending on the medium mean Z number and density (over correction), and a artifactual 'activity' in the denser 'cold' vial (incorrect attenuation correction. The dense saccharose solutions, with non elevated Z number, do not affect the CT attenuation correction. (authors)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-07-29

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

  3. Attenuation and scattering tomography of the deep plumbing system of Mount St. Helens

    Science.gov (United States)

    De Siena, Luca; Thomas, Christine; Waite, Greg P.; Moran, Seth C.; Klemme, Stefan

    2014-01-01

    We present a combined 3-D P wave attenuation, 2-D S coda attenuation, and 3-D S coda scattering tomography model of fluid pathways, feeding systems, and sediments below Mount St. Helens (MSH) volcano between depths of 0 and 18 km. High-scattering and high-attenuation shallow anomalies are indicative of magma and fluid-rich zones within and below the volcanic edifice down to 6 km depth, where a high-scattering body outlines the top of deeper aseismic velocity anomalies. Both the volcanic edifice and these structures induce a combination of strong scattering and attenuation on any seismic wavefield, particularly those recorded on the northern and eastern flanks of the volcanic cone. North of the cone between depths of 0 and 10 km, a low-velocity, high-scattering, and high-attenuation north-south trending trough is attributed to thick piles of Tertiary marine sediments within the St. Helens Seismic Zone. A laterally extended 3-D scattering contrast at depths of 10 to 14 km is related to the boundary between upper and lower crust and caused in our interpretation by the large-scale interaction of the Siletz terrane with the Cascade arc crust. This contrast presents a low-scattering, 4–6 km2 “hole” under the northeastern flank of the volcano. We infer that this section represents the main path of magma ascent from depths greater than 6 km at MSH, with a small north-east shift in the lower plumbing system of the volcano. We conclude that combinations of different nonstandard tomographic methods, leading toward full-waveform tomography, represent the future of seismic volcano imaging.

  4. 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

  5. Attenuation correction for brain PET imaging using deep neural network based on dixon and ZTE MR images.

    Science.gov (United States)

    Gong, Kuang; Yang, Jaewon; Kim, Kyungsang; El Fakhri, Georges; Seo, Youngho; Li, Quanzheng

    2018-05-23

    Positron Emission Tomography (PET) is a functional imaging modality widely used in neuroscience studies. To obtain meaningful quantitative results from PET images, attenuation correction is necessary during image reconstruction. For PET/MR hybrid systems, PET attenuation is challenging as Magnetic Resonance (MR) images do not reflect attenuation coefficients directly. To address this issue, we present deep neural network methods to derive the continuous attenuation coefficients for brain PET imaging from MR images. With only Dixon MR images as the network input, the existing U-net structure was adopted and analysis using forty patient data sets shows it is superior than other Dixon based methods. When both Dixon and zero echo time (ZTE) images are available, we have proposed a modified U-net structure, named GroupU-net, to efficiently make use of both Dixon and ZTE information through group convolution modules when the network goes deeper. Quantitative analysis based on fourteen real patient data sets demonstrates that both network approaches can perform better than the standard methods, and the proposed network structure can further reduce the PET quantification error compared to the U-net structure. © 2018 Institute of Physics and Engineering in Medicine.

  6. Characterization of southern yellow pine bark layers by Attenuated Total Reflectance (ATR) and Fourier Transform Infrared (FT-IR) Spectroscopy

    Science.gov (United States)

    Thomas L. Eberhardt

    2009-01-01

    The outer bark (rhytidome) of the southern yellow pines is a complex structure comprised of alternating layers of obliterated phloem and periderm tissues, with the latter comprised of three layers, those being phellem, phellogen, and phelloderm. An attenuated total reflectance (ATR) sampling accessory, coupled with a Fourier transform infrared (FTIR) spectrometer,...

  7. 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

  8. Rosiglitazone attenuates pulmonary fibrosis and radiation-induced intestinal damage

    International Nuclear Information System (INIS)

    Mangoni, M.; Gerini, C.; Sottili, M.; Cassani, S.; Stefania, G.; Biti, G.; Castiglione, F.; Vanzi, E.; Bottoncetti, A.; Pupi, A.

    2011-01-01

    Full text of publication follows: Purpose.-The aim of the study was to evaluate radioprotective effect of rosiglitazone (RGZ) on a murine model of late pulmonary damage and of acute intestinal damage. Methods.- Lung fibrosis: C57 mice were treated with the radiomimetic agent bleomycin, with or without rosiglitazone (5 mg/kg/day). To obtain an independent qualitative and quantitative measure for lung fibrosis we used high resolution CT, performed twice a week during the entire observation period. Hounsfield Units (HU) of section slides from the upper and lower lung region were determined. On day 31 lungs were collected for histological analysis. Acute intestinal damage: mice underwent 12 Gy total body irradiation with or without rosiglitazone. Mice were sacrificed 24 or 72 h after total body irradiation and ileum and colon were collected. Results.- Lung fibrosis: after bleomycin treatment, mice showed typical CT features of lung fibrosis, including irregular septal thickening and patchy peripheral reticular abnormalities. Accordingly, HU lung density was dramatically increased. Rosiglitazone markedly attenuated the radiological signs of fibrosis and strongly inhibited HU lung density increase (60% inhibition at the end of the observation period). Histological analysis revealed that in bleomycin-treated mice, fibrosis involved 50-55% of pulmonary parenchyma and caused an alteration of the alveolar structures in 10% of parenchyma, while in rosiglitazone-treated mice, fibrosis involved only 20-25% of pulmonary parenchyma, without alterations of the alveolar structures. Acute intestinal damage: 24 h after 12 Gy of total body irradiation intestinal mucosa showed villi shortening, mucosal thickness and crypt necrotic changes. Rosiglitazone showed a histological improvement of tissue structure, with villi and crypts normalization and oedema reduction. Conclusion.- These results demonstrate that rosiglitazone displays a protective effect on pulmonary fibrosis and radiation

  9. Rosiglitazone attenuates pulmonary fibrosis and radiation-induced intestinal damage

    Energy Technology Data Exchange (ETDEWEB)

    Mangoni, M.; Gerini, C.; Sottili, M.; Cassani, S.; Stefania, G.; Biti, G. [Radiotherapy Unit, Clinical Physiopathology Department, University of Florence, Firenze (Italy); Castiglione, F. [Department of Human Pathology and Oncology, University of Florence, Firenze (Italy); Vanzi, E.; Bottoncetti, A.; Pupi, A. [Nuclear Medicine Unit, Clinical Physiopathology Department, University of Florence, Firenze (Italy)

    2011-10-15

    Full text of publication follows: Purpose.-The aim of the study was to evaluate radioprotective effect of rosiglitazone (RGZ) on a murine model of late pulmonary damage and of acute intestinal damage. Methods.- Lung fibrosis: C57 mice were treated with the radiomimetic agent bleomycin, with or without rosiglitazone (5 mg/kg/day). To obtain an independent qualitative and quantitative measure for lung fibrosis we used high resolution CT, performed twice a week during the entire observation period. Hounsfield Units (HU) of section slides from the upper and lower lung region were determined. On day 31 lungs were collected for histological analysis. Acute intestinal damage: mice underwent 12 Gy total body irradiation with or without rosiglitazone. Mice were sacrificed 24 or 72 h after total body irradiation and ileum and colon were collected. Results.- Lung fibrosis: after bleomycin treatment, mice showed typical CT features of lung fibrosis, including irregular septal thickening and patchy peripheral reticular abnormalities. Accordingly, HU lung density was dramatically increased. Rosiglitazone markedly attenuated the radiological signs of fibrosis and strongly inhibited HU lung density increase (60% inhibition at the end of the observation period). Histological analysis revealed that in bleomycin-treated mice, fibrosis involved 50-55% of pulmonary parenchyma and caused an alteration of the alveolar structures in 10% of parenchyma, while in rosiglitazone-treated mice, fibrosis involved only 20-25% of pulmonary parenchyma, without alterations of the alveolar structures. Acute intestinal damage: 24 h after 12 Gy of total body irradiation intestinal mucosa showed villi shortening, mucosal thickness and crypt necrotic changes. Rosiglitazone showed a histological improvement of tissue structure, with villi and crypts normalization and oedema reduction. Conclusion.- These results demonstrate that rosiglitazone displays a protective effect on pulmonary fibrosis and radiation

  10. Endogenous cueing attenuates object substitution masking.

    Science.gov (United States)

    Germeys, Filip; Pomianowska, I; De Graef, P; Zaenen, P; Verfaillie, K

    2010-07-01

    Object substitution masking (OSM) is a form of visual masking in which a briefly presented target surrounded by four small dots is masked by the continuing presence of the four dots after target offset. A major parameter in the prediction of OSM is the time required for attention to be directed to the target following its onset. Object substitution theory (Di Lollo et al. in J Exp Psychol Gen 129:481-507, 2000) predicts that the sooner attention can be focused at the target's location, the less masking will ensue. However, recently Luiga and Bachmann (Psychol Res 71:634-640, 2007) presented evidence that precueing of attention to the target location prior to target-plus-mask onset by means of a central (endogenous) arrow cue does not reduce OSM. When attention was cued exogenously, OSM was attenuated. Based on these results, Luiga and Bachmann argued that object substitution theory should be adapted by differentiating the ways of directing attention to the target location. The goal of the present study was to further examine the dissociation between the effects of endogenous and exogenous precueing on OSM. Contrary to Luiga and Bachmann, our results show that prior shifts of attention to the target location initiated by both exogenous and endogenous cues reduce OSM as predicted by object substitution theory and its computational model CMOS.

  11. Silibinin attenuates allergic airway inflammation in mice

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Yun Ho [Department of Anatomy, Medical School, Institute for Medical Sciences, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of); Jin, Guang Yu [Department of Radiology, Yanbian University Hospital, YanJi 133002 (China); Guo, Hui Shu [Centralab, The First Affiliated Hospital of Dalian Medical University, Dalian 116011 (China); Piao, Hong Mei [Department of Respiratory Medicine, Yanbian University Hospital, YanJi 133000 (China); Li, Liang chang; Li, Guang Zhao [Department of Anatomy and Histology and Embryology, Yanbian University School of Basic Medical Sciences, 977 Gongyuan Road, YanJi 133002, Jilin (China); Lin, Zhen Hua [Department of Pathology, Yanbian University School of Basic Medical Sciences, YanJi 133000 (China); Yan, Guang Hai, E-mail: ghyan@ybu.edu.cn [Department of Anatomy and Histology and Embryology, Yanbian University School of Basic Medical Sciences, 977 Gongyuan Road, YanJi 133002, Jilin (China)

    2012-10-26

    Highlights: Black-Right-Pointing-Pointer Silibinin diminishes ovalbumin-induced inflammatory reactions in the mouse lung. Black-Right-Pointing-Pointer Silibinin reduces the levels of various cytokines into the lung of allergic mice. Black-Right-Pointing-Pointer Silibinin prevents the development of airway hyperresponsiveness in allergic mice. Black-Right-Pointing-Pointer Silibinin suppresses NF-{kappa}B transcriptional activity. -- Abstract: Allergic asthma is a chronic inflammatory disease regulated by coordination of T-helper2 (Th2) type cytokines and inflammatory signal molecules. Silibinin is one of the main flavonoids produced by milk thistle, which is reported to inhibit the inflammatory response by suppressing the nuclear factor-kappa B (NF-{kappa}B) pathway. Because NF-{kappa}B activation plays a pivotal role in the pathogenesis of allergic inflammation, we have investigated the effect of silibinin on a mouse ovalbumin (OVA)-induced asthma model. Airway hyperresponsiveness, cytokines levels, and eosinophilic infiltration were analyzed in bronchoalveolar lavage fluid and lung tissue. Pretreatment of silibinin significantly inhibited airway inflammatory cell recruitment and peribronchiolar inflammation and reduced the production of various cytokines in bronchoalveolar fluid. In addition, silibinin prevented the development of airway hyperresponsiveness and attenuated the OVA challenge-induced NF-{kappa}B activation. These findings indicate that silibinin protects against OVA-induced airway inflammation, at least in part via downregulation of NF-{kappa}B activity. Our data support the utility of silibinin as a potential medicine for the treatment of asthma.

  12. Silibinin attenuates allergic airway inflammation in mice

    International Nuclear Information System (INIS)

    Choi, Yun Ho; Jin, Guang Yu; Guo, Hui Shu; Piao, Hong Mei; Li, Liang chang; Li, Guang Zhao; Lin, Zhen Hua; Yan, Guang Hai

    2012-01-01

    Highlights: ► Silibinin diminishes ovalbumin-induced inflammatory reactions in the mouse lung. ► Silibinin reduces the levels of various cytokines into the lung of allergic mice. ► Silibinin prevents the development of airway hyperresponsiveness in allergic mice. ► Silibinin suppresses NF-κB transcriptional activity. -- Abstract: Allergic asthma is a chronic inflammatory disease regulated by coordination of T-helper2 (Th2) type cytokines and inflammatory signal molecules. Silibinin is one of the main flavonoids produced by milk thistle, which is reported to inhibit the inflammatory response by suppressing the nuclear factor-kappa B (NF-κB) pathway. Because NF-κB activation plays a pivotal role in the pathogenesis of allergic inflammation, we have investigated the effect of silibinin on a mouse ovalbumin (OVA)-induced asthma model. Airway hyperresponsiveness, cytokines levels, and eosinophilic infiltration were analyzed in bronchoalveolar lavage fluid and lung tissue. Pretreatment of silibinin significantly inhibited airway inflammatory cell recruitment and peribronchiolar inflammation and reduced the production of various cytokines in bronchoalveolar fluid. In addition, silibinin prevented the development of airway hyperresponsiveness and attenuated the OVA challenge-induced NF-κB activation. These findings indicate that silibinin protects against OVA-induced airway inflammation, at least in part via downregulation of NF-κB activity. Our data support the utility of silibinin as a potential medicine for the treatment of asthma.

  13. Ursodeoxycholic acid attenuates colonic epithelial secretory function

    Science.gov (United States)

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

    2013-01-01

    Dihydroxy bile acids, such as chenodeoxycholic acid (CDCA), are well known to promote colonic fluid and electrolyte secretion, thereby causing diarrhoea associated with bile acid malabsorption. However, CDCA is rapidly metabolised by colonic bacteria to ursodeoxycholic acid (UDCA), the effects of which on epithelial transport are poorly characterised. Here, we investigated the role of UDCA in the regulation of colonic epithelial secretion. Cl− secretion was measured across voltage-clamped monolayers of T84 cells and muscle-stripped sections of mouse or human colon. Cell surface biotinylation was used to assess abundance/surface expression of transport proteins. Acute (15 min) treatment of T84 cells with bilateral UDCA attenuated Cl− secretory responses to the Ca2+ and cAMP-dependent secretagogues carbachol (CCh) and forskolin (FSK) to 14.0 ± 3.8 and 40.2 ± 7.4% of controls, respectively (n= 18, P acid (LCA). Accordingly, LCA (50–200 μm) enhanced agonist-induced secretory responses in vitro and a metabolically stable UDCA analogue, 6α-methyl-UDCA, exerted anti-secretory actions in vitro and in vivo. In conclusion, UDCA exerts direct anti-secretory actions on colonic epithelial cells and metabolically stable derivatives of the bile acid may offer a new approach for treating intestinal diseases associated with diarrhoea. PMID:23507881

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

    Science.gov (United States)

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

  15. Reconstruction of multiple line source attenuation maps

    International Nuclear Information System (INIS)

    Celler, A.; Sitek, A.; Harrop, R.

    1996-01-01

    A simple configuration for a transmission source for the single photon emission computed tomography (SPECT) was proposed, which utilizes a series of collimated line sources parallel to the axis of rotation of a camera. The detector is equipped with a standard parallel hole collimator. We have demonstrated that this type of source configuration can be used to generate sufficient data for the reconstruction of the attenuation map when using 8-10 line sources spaced by 3.5-4.5 cm for a 30 x 40cm detector at 65cm distance from the sources. Transmission data for a nonuniform thorax phantom was simulated, then binned and reconstructed using filtered backprojection (FBP) and iterative methods. The optimum maps are obtained with data binned into 2-3 bins and FBP reconstruction. The activity in the source was investigated for uniform and exponential activity distributions, as well as the effect of gaps and overlaps of the neighboring fan beams. A prototype of the line source has been built and the experimental verification of the technique has started

  16. Transient hepatic attenuation differences in neonates

    International Nuclear Information System (INIS)

    Towbin, Alexander J.; Fleck, Robert; Ying, Jun

    2009-01-01

    A transient hepatic attenuation difference (THAD) is a hepatic perfusion anomaly seen on contrast-enhanced CT scans caused by an alteration in the dual blood supply of the liver. Although THADs have been described in adolescents and adults, they have not previously been described in neonates. We describe the appearance and evaluate the frequency of THADs in neonates ≤1 month of age compared to other infants younger than 2 years. A retrospective study was performed looking at all CT angiograms from 2000 to 2007 in infants <2 years of age. The incidence of THADs was compared among four age groups. Significance was determined using a logistic regression model. The study included 128 CT angiograms. A THAD was seen in 9/26 infants <1 month of age, in 3/50 infants 1 to 6 months of age, in 1/23 infants 6 months to 1 year of age, and in 1/29 infants 1 to 2 years of age. A THAD was found significantly more frequently in infants <1 month of age than in the older age groups (P<0.05). THADs are benign entities that can be seen normally in the neonatal age group. When the characteristic appearance is seen on CT, no further imaging is needed. (orig.)

  17. Agmatine attenuates silica-induced pulmonary fibrosis.

    Science.gov (United States)

    El-Agamy, D S; Sharawy, M H; Ammar, E M

    2014-06-01

    There is a large body of evidence that nitric oxide (NO) formation is implicated in mediating silica-induced pulmonary fibrosis. As a reactive free radical, NO may not only contribute to lung parenchymal tissue injury but also has the ability to combine with superoxide and form a highly reactive toxic species peroxynitrite that can induce extensive cellular toxicity in the lung tissues. This study aimed to explore the effect of agmatine, a known NO synthase inhibitor, on silica-induced pulmonary fibrosis in rats. Male Sprague Dawley rats were treated with agmatine for 60 days following a single intranasal instillation of silica suspension (50 mg in 0.1 ml saline/rat). The results revealed that agmatine attenuated silica-induced lung inflammation as it decreased the lung wet/dry weight ratio, protein concentration, and the accumulation of the inflammatory cells in the bronchoalveolar lavage fluid. Agmatine showed antifibrotic activity as it decreased total hydroxyproline content of the lung and reduced silica-mediated lung inflammation and fibrosis in lung histopathological specimen. In addition, agmatine significantly increased superoxide dismutase (p Agmatine also reduced silica-induced overproduction of pulmonary nitrite/nitrate as well as tumor necrosis factor α. Collectively, these results demonstrate the protective effects of agmatine against the silica-induced lung fibrosis that may be attributed to its ability to counteract the NO production, lipid peroxidation, and regulate cytokine effects. © The Author(s) 2014.

  18. Statins attenuate polymethylmethacrylate-mediated monocyte activation.

    LENUS (Irish Health Repository)

    Laing, Alan J

    2012-02-03

    BACKGROUND: Periprosthetic osteolysis precipitates aseptic loosening of components, increases the risk of periprosthetic fracture and, through massive bone loss, complicates revision surgery and ultimately is the primary cause for failure of joint arthroplasty. The anti-inflammatory properties of HMG-CoA reductase inhibitors belonging to the statin family are well recognized. We investigated a possible role for status in initiating the first stage of the osteolytic cycle, namely monocytic activation. METHODS: We used an in vitro model of the human monocyte\\/macrophage inflammatory response to poly-methylmethacrylate (PMMA) particles after pretreat-ing cells with cerivastatin, a potent member of the statin family. Cell activation based upon production of TNF-alpha and MCP-1 cytokines was analyzed and the intracellular Raf-MEK-ERK signal transduction pathway was evaluated using western blot analysis, to identify its role in cell activation and in any cerivastatin effects observed. RESULTS: We found that pretreatment with cerivastatin significantly abrogates the production of inflammatory cytokines TNF-alpha and MCP-1 by human monocytes in response to polymethylmethacrylate particle activation. This inflammatory activation and attenuation appear to be mediated through the intracellular Raf-MEK-ERK pathway. INTERPRETATION: We propose that by intervening at the upstream activation stage, subsequent osteoclast activation and osteolysis can be suppressed. We believe that the anti-inflammatory properties of statins may potentially play a prophylactic role in the setting of aseptic loosening, and in so doing increase implant longevity.

  19. Minocycline Attenuates Iron-Induced Brain Injury.

    Science.gov (United States)

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

    2016-01-01

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

  20. Obesity attenuates gender differences in cardiovascular mortality.

    Science.gov (United States)

    Song, Xin; Tabák, Adam G; Zethelius, Björn; Yudkin, John S; Söderberg, Stefan; Laatikainen, Tiina; Stehouwer, Coen D A; Dankner, Rachel; Jousilahti, Pekka; Onat, Altan; Nilsson, Peter M; Satman, Ilhan; Vaccaro, Olga; Tuomilehto, Jaakko; Qiao, Qing

    2014-10-19

    To estimate cardiovascular disease (CVD) mortality in relation to obesity and gender. Data from 11 prospective cohorts from four European countries including 23 629 men and 21 965 women, aged 24 to 99 years, with a median follow-up of 7.9 years were analyzed. Hazards ratios (HR) for CVD mortality in relation to baseline body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR) and waist-to-height ratio (WHtR) were estimated using Cox proportional hazards models with age as the timescale. Men had higher CVD mortality than women in all four BMI categories (obesity defined by WC, WHR or WHtR. The gender difference was slightly smaller in obese than in non-obese individuals; but the interaction was statistically significant only between gender and WC (p = 0.02), and WHtR (p = 0.01). None of the interaction terms was significant among non-diabetic individuals. Men had higher CVD mortality than women across categories of anthropometric measures of obesity. The gender difference was attenuated in obese individuals, which warrants further investigation.

  1. Features of HF Radio Wave Attenuation in the Midlatitude Ionosphere Near the Skip Zone Boundary

    Science.gov (United States)

    Denisenko, P. F.; Skazik, A. I.

    2017-06-01

    We briefly describe the history of studying the decameter radio wave attenuation by different methods in the midlatitude ionosphere. A new method of estimating the attenuation of HF radio waves in the ionospheric F region near the skip zone boundary is presented. This method is based on an analysis of the time structure of the interference field generated by highly stable monochromatic X-mode radio waves at the observation point. The main parameter is the effective electron collision frequency νeff, which allows for all energy losses in the form of equivalent heat loss. The frequency νeff is estimated by matching the assumed (model) and the experimentally observed structures. Model calculations are performed using the geometrical-optics approximation. The spatial attenuation caused by the influence of the medium-scale traveling ionospheric disturbances is taken into account. Spherical shape of the ionosphere and the Earth's magnetic field are roughly allowed for. The results of recording of the level of signals from the RWM (Moscow) station at a frequency of 9.996 MHz at point Rostov are used.

  2. What makes ribosome-mediated transcriptional attenuation sensitive to amino acid limitation?

    Directory of Open Access Journals (Sweden)

    Johan Elf

    2005-06-01

    Full Text Available Ribosome-mediated transcriptional attenuation mechanisms are commonly used to control amino acid biosynthetic operons in bacteria. The mRNA leader of such an operon contains an open reading frame with "regulatory" codons, cognate to the amino acid that is synthesized by the enzymes encoded by the operon. When the amino acid is in short supply, translation of the regulatory codons is slow, which allows transcription to continue into the structural genes of the operon. When amino acid supply is in excess, translation of regulatory codons is rapid, which leads to termination of transcription. We use a discrete master equation approach to formulate a probabilistic model for the positioning of the RNA polymerase and the ribosome in the attenuator leader sequence. The model describes how the current rate of amino acid supply compared to the demand in protein synthesis (signal determines the expression of the amino acid biosynthetic operon (response. The focus of our analysis is on the sensitivity of operon expression to a change in the amino acid supply. We show that attenuation of transcription can be hyper-sensitive for two main reasons. The first is that its response depends on the outcome of a race between two multi-step mechanisms with synchronized starts: transcription of the leader of the operon, and translation of its regulatory codons. The relative change in the probability that transcription is aborted (attenuated can therefore be much larger than the relative change in the time it takes for the ribosome to read a regulatory codon. The second is that the general usage frequencies of codons of the type used in attenuation control are small. A small percentage decrease in the rate of supply of the controlled amino acid can therefore lead to a much larger percentage decrease in the rate of reading a regulatory codon. We show that high sensitivity further requires a particular choice of regulatory codon among several synonymous codons for the

  3. Osteopontin attenuates aging-associated phenotypes of hematopoietic stem cells.

    Science.gov (United States)

    Guidi, Novella; Sacma, Mehmet; Ständker, Ludger; Soller, Karin; Marka, Gina; Eiwen, Karina; Weiss, Johannes M; Kirchhoff, Frank; Weil, Tanja; Cancelas, Jose A; Florian, Maria Carolina; Geiger, Hartmut

    2017-04-03

    Upon aging, hematopoietic stem cells (HSCs) undergo changes in function and structure, including skewing to myeloid lineages, lower reconstitution potential and loss of protein polarity. While stem cell intrinsic mechanisms are known to contribute to HSC aging, little is known on whether age-related changes in the bone marrow niche regulate HSC aging. Upon aging, the expression of osteopontin (OPN) in the murine bone marrow stroma is reduced. Exposure of young HSCs to an OPN knockout niche results in a decrease in engraftment, an increase in long-term HSC frequency and loss of stem cell polarity. Exposure of aged HSCs to thrombin-cleaved OPN attenuates aging of old HSCs, resulting in increased engraftment, decreased HSC frequency, increased stem cell polarity and a restored balance of lymphoid and myeloid cells in peripheral blood. Thus, our data suggest a critical role for reduced stroma-derived OPN for HSC aging and identify thrombin-cleaved OPN as a novel niche informed therapeutic approach for ameliorating HSC phenotypes associated with aging. © 2017 The Authors. Published under the terms of the CC BY NC ND 4.0 license.

  4. 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.

  5. 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.

  6. Technological cost-reduction pathways for attenuator wave energy converters in the marine hydrokinetic environment.

    Energy Technology Data Exchange (ETDEWEB)

    Bull, Diana L; Ochs, Margaret Ellen

    2013-09-01

    This report considers and prioritizes the primary potential technical costreduction pathways for offshore wave activated body attenuators designed for ocean resources. This report focuses on technical research and development costreduction pathways related to the device technology rather than environmental monitoring or permitting opportunities. Three sources of information were used to understand current cost drivers and develop a prioritized list of potential costreduction pathways: a literature review of technical work related to attenuators, a reference device compiled from literature sources, and a webinar with each of three industry device developers. Data from these information sources were aggregated and prioritized with respect to the potential impact on the lifetime levelized cost of energy, the potential for progress, the potential for success, and the confidence in success. Results indicate the five most promising costreduction pathways include advanced controls, an optimized structural design, improved power conversion, planned maintenance scheduling, and an optimized device profile.

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

    International Nuclear Information System (INIS)

    Muller-Runkel, R.; Vijayakumar, S.

    1986-01-01

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

  8. An Aminopyridazine Inhibitor of Death Associated Protein Kinase Attenuates Hypoxia-Ischemia Induced Brain Damage

    Energy Technology Data Exchange (ETDEWEB)

    Velentza, A.V.; Wainwright, M.S.; Zasadzki, M.; Mirzoeva, S.; Haiech, J.; Focia, P.J.; Egli, M.; Watterson, D.M.

    2010-03-08

    Death associated protein kinase (DAPK) is a calcium and calmodulin regulated enzyme that functions early in eukaryotic programmed cell death, or apoptosis. To validate DAPK as a potential drug discovery target for acute brain injury, the first small molecule DAPK inhibitor was synthesized and tested in vivo. A single injection of the aminopyridazine-based inhibitor administered 6 h after injury attenuated brain tissue or neuronal biomarker loss measured, respectively, 1 week and 3 days later. Because aminopyridazine is a privileged structure in neuropharmacology, we determined the high-resolution crystal structure of a binary complex between the kinase domain and a molecular fragment of the DAPK inhibitor. The co-crystal structure describes a structural basis for interaction and provides a firm foundation for structure-assisted design of lead compounds with appropriate molecular properties for future drug development.

  9. Attenuation of Recombinant Yellow Fever 17D Viruses Expressing Foreign Protein Epitopes at the Surface

    Science.gov (United States)

    Bonaldo, Myrna C.; Garratt, Richard C.; Marchevsky, Renato S.; Coutinho, Evandro S. F.; Jabor, Alfredo V.; Almeida, Luís F. C.; Yamamura, Anna M. Y.; Duarte, Adriana S.; Oliveira, Prisciliana J.; Lizeu, Jackeline O. P.; Camacho, Luiz A. B.; Freire, Marcos S.; Galler, Ricardo

    2005-01-01

    The yellow fever (YF) 17D vaccine is a live attenuated virus. Three-dimensional (3D) homology modeling of the E protein structure from YF 17D virus and its comparison with that from tick-borne encephalitis virus revealed that it is possible to accommodate inserts of different sizes and amino acid compositions in the flavivirus E protein fg loop. This is consistent with the 3D structures of both the dimeric and trimeric forms in which the fg loop lies exposed to solvents. We demonstrate here that YF 17D viruses bearing foreign humoral (17D/8) and T-cell (17D/13) epitopes, which vary in sequence and length, displayed growth restriction. It is hypothesized that interference with the dimer-trimer transition and with the formation of a ring of such trimers in order to allow fusion compromises the capability of the E protein to induce fusion of viral and endosomal membranes, and a slower rate of fusion may delay the extent of virus production. This would account for the lower levels of replication in cultured cells and of viremia in monkeys, as well as for the more attenuated phenotype of the recombinant viruses in monkeys. Testing of both recombinant viruses (17D/8 and 17D/13) for monkey neurovirulence also suggests that insertion at the 17D E protein fg loop does not compromise the attenuated phenotype of YF 17D virus, further confirming the potential use of this site for the development of new live attenuated 17D virus-based vaccines. PMID:15956601

  10. 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)

  11. 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.

  12. Telmisartan attenuates diabetes induced depression in rats.

    Science.gov (United States)

    Aswar, Urmila; Chepurwar, Shilpa; Shintre, Sumit; Aswar, Manoj

    2017-04-01

    Role of brain renin angiotensin system (RAS) is well understood and various clinical studies have proposed neuroprotective effects of ARB's. It is also assumed that diabetic depression is associated with activation of brain RAS, HPA axis dysregulation and brain inflammatory events. Therefore, the present study was designed to investigate the antidepressant effect of low dose telmisartan (TMS) in diabetes induced depression (DID) in rats. Diabetes was induced by injecting streptozotocin. After 21days of treatment the rats were subjected to forced swim test (FST). The rats, with increased immobility time, were considered depressed and were treated with vehicle or TMS (0.05mg/kg, po) or metformin (200mg/kg, po) or fluoxetine (20mg/kg, po). A separate group was also maintained to study the combination of metformin and TMS. At the end of 21days of treatments, FST, open field test (OFT) and elevated plus maze (EPM) paradigm were performed. Blood was drawn to estimate serum cortisol, nitric oxide (NO), interleukin-6 (IL-6) and interleukin-1β (IL-1β). Persistent hyperglycemia resulted in depression and anxiety in rats as observed by increased immobility, reduced latency for immobility, reduced open arm entries and time spent. The depressed rats showed a significant rise in serum cortisol, NO, IL-6 and IL-1β (pdepression and anxiety. It also significantly attenuated serum cortisol, NO, IL-6 and IL-1β (pdepressive mood, reduces pro-inflammatory mediators and ameliorates the HPA axis function; thereby providing beneficial effects in DID. Copyright © 2016. Published by Elsevier Urban & Partner Sp. z o.o.

  13. 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)

  14. P-wave attenuation in the Pacific slab beneath northeastern Japan revealed by the spectral ratio of intraslab earthquakes

    Science.gov (United States)

    Shiina, Takahiro; Nakajima, Junichi; Matsuzawa, Toru

    2018-05-01

    We investigate P-wave attenuation, Qp-1, in the Pacific slab beneath northeastern (NE) Japan, adopting for the first time the spectral ratio technique for intraslab earthquakes. When seismograms of two earthquakes are recorded at a station and their ray paths to the station are largely overlapped, station-dependent amplification and structural effects on the overlapped rays can be canceled out from the ratio of the spectral amplitudes of the seismograms. Therefore, adopting the spectral ratio technique for intraslab earthquakes has a great advantage for the precise evaluation of Qp-1 in the slab because the structural effects above the slab, including the high-attenuation mantle wedge, are removed. For estimating the intraslab Qp-1, we determined corner frequency of the intraslab earthquakes using the S-coda wave spectral ratio as the first step. Then, we evaluated the inter-event path attenuation, Δt*, from the ratio of the spectral amplitudes of P waves. The obtained result shows that P-wave attenuation in the Pacific slab marks Qp-1 of 0.0015 (Qp of ∼670) at depths of 50-250 km. This indicates that the P-wave attenuation in the Pacific slab is weaker than that in the mantle wedge. The relatively high-Qp-1 is correlated with the distributions of intraslab earthquakes, suggesting that the P-wave amplitude is more attenuated around active seismicity zones in the slab. Therefore, our observations likely indicate the presence of fractures, hydrous minerals, and dehydrated fluid around seismogenic zones in the slab at intermediate depths.

  15. Coffee Consumption Attenuates Insulin Resistance and Glucose ...

    African Journals Online (AJOL)

    olayemitoyin

    Alzheimer's disease (CBS 2012), dementia (Health news 2012) and ... the effects of coffee on insulin resistance and glucose tolerance as ..... mortality among patients with type 2 diabetes. ... transporter family: Structure, function and tissue-.

  16. 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

  17. 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

  18. 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

  19. 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....

  20. Multi-resolution inversion algorithm for the attenuated radon transform

    KAUST Repository

    Barbano, Paolo Emilio; Fokas, Athanasios S.

    2011-01-01

    We present a FAST implementation of the Inverse Attenuated Radon Transform which incorporates accurate collimator response, as well as artifact rejection due to statistical noise and data corruption. This new reconstruction procedure is performed

  1. Numerical Speadsheet Modeling of Natural Attenuation for Groundwater Contaminant Plumes

    National Research Council Canada - National Science Library

    Twesme, Troy

    1999-01-01

    .... The model was used to evaluate natural attenuation for removal of a trichloroethylene (TCE) plume from a surficial aquifer containing three regions with distinctly different processes for degradation of TCE...

  2. 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)

  3. 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)

  4. 2 original article non-attenuation of highly pathogenic avian

    African Journals Online (AJOL)

    Dr Oboro VO

    AFRICAN JOURNAL OF CLINICAL AND EXPERIMENTAL MICROBIOLOGY JANUARY 2010. ISBN 1595-689X ... NON-ATTENUATION OF HIGHLY PATHOGENIC AVIAN INFLUENZA. H5N1 BY .... Diagnostic PCR was conducted to determine ...

  5. 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

  6. Natural Attenuation of the Persistent Chemical Warfare Agent ...

    Science.gov (United States)

    Report This project studied the influence of temperature on the natural attenuation of VX from five types of porous/permeable materials: unsealed concrete, plywood, rubber escalator handrail, high density polyethylene (HDPE) plastic, and acoustic ceiling tile.

  7. An acoustic eikonal equation for attenuating VTI media

    KAUST Repository

    Hao, Qi; Alkhalifah, Tariq Ali

    2016-01-01

    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

  8. An acoustic eikonal equation for attenuating orthorhombic media

    KAUST Repository

    Hao, Qi; Alkhalifah, Tariq Ali

    2017-01-01

    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

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. Nuclear equipment to determine soil and water mass attenuation coefficients

    International Nuclear Information System (INIS)

    Zucchi, O.L.A.D.; Nascimento Filho, V.F. do

    1984-01-01

    The feasibility of substituting the monochannel gamma spectrometer, traditionally used in the gamma ray attenuation technique, for a less sophisticated and less expensive system of integral counting is studied. The proposed system can be operated by a non-specialized person. Three detection systems were used in the determination of the mass attenuation coefficients for different types of soil and for water. (M.A.C.) [pt

  14. 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.

  15. 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

  16. 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.

  17. Broad beam X-rays attenuation in silicum glass

    International Nuclear Information System (INIS)

    Risticj, Dj.; Vukovicj, S.; Markovicj, P.

    1987-01-01

    Using broad beam geometry the attenuation for domestic silicum glass have been studied for constant X-ray potentials from 50 to 150 kV. The density of the silicium glass was 2,5x10 3 kg/m 3 . From the attenuation curves the half value layers were obtained. The use of this glass as the biological shield is pointed out. (author). 2 refs.; 2 tabs.; 2 figs

  18. Transcranial Alternating Current Stimulation Attenuates Neuronal Adaptation.

    Science.gov (United States)

    Kar, Kohitij; Duijnhouwer, Jacob; Krekelberg, Bart

    2017-03-01

    We previously showed that brief application of 2 mA (peak-to-peak) transcranial currents alternating at 10 Hz significantly reduces motion adaptation in humans. This is but one of many behavioral studies showing that weak currents applied to the scalp modulate neural processing. Transcranial stimulation has been shown to improve perception, learning, and a range of clinical symptoms. Few studies, however, have measured the neural consequences of transcranial current stimulation. We capitalized on the strong link between motion perception and neural activity in the middle temporal (MT) area of the macaque monkey to study the neural mechanisms that underlie the behavioral consequences of transcranial alternating current stimulation. First, we observed that 2 mA currents generated substantial intracranial fields, which were much stronger in the stimulated hemisphere (0.12 V/m) than on the opposite side of the brain (0.03 V/m). Second, we found that brief application of transcranial alternating current stimulation at 10 Hz reduced spike-frequency adaptation of MT neurons and led to a broadband increase in the power spectrum of local field potentials. Together, these findings provide a direct demonstration that weak electric fields applied to the scalp significantly affect neural processing in the primate brain and that this includes a hitherto unknown mechanism that attenuates sensory adaptation. SIGNIFICANCE STATEMENT Transcranial stimulation has been claimed to improve perception, learning, and a range of clinical symptoms. Little is known, however, how transcranial current stimulation generates such effects, and the search for better stimulation protocols proceeds largely by trial and error. We investigated, for the first time, the neural consequences of stimulation in the monkey brain. We found that even brief application of alternating current stimulation reduced the effects of adaptation on single-neuron firing rates and local field potentials; this mechanistic

  19. 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.

  20. 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.

  1. 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)

  2. 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

  3. Teleseismic P and S wave attenuation constraints on temperature and melt of the upper mantle in the Alaska Subduction Zone.

    Science.gov (United States)

    Soto Castaneda, R. A.; Abers, G. A.; Eilon, Z.; Christensen, D. H.

    2017-12-01

    Recent broadband deployments in Alaska provide an excellent opportunity to advance our understanding of the Alaska-Aleutians subduction system, with implications for subduction processes worldwide. Seismic attenuation, measured from teleseismic body waves, provides a strong constraint on thermal structure as well as an indirect indication of ground shaking expected from large intermediate-depth earthquakes. We measure P and S wave attenuation from pairwise amplitude and phase spectral ratios for teleseisms recorded at 204 Transportable Array, Alaska Regional, and Alaska Volcano Observatory, SALMON (Southern Alaska Lithosphere & Mantle Observation Network) and WVLF (Wrangell Volcanics & subducting Lithosphere Fate) stations in central Alaska. The spectral ratios are inverted in a least squares sense for differential t* (path-averaged attenuation operator) and travel time anomalies at every station. Our preliminary results indicate a zone of low attenuation across the forearc and strong attenuation beneath arc and backarc in the Cook Inlet-Kenai region where the Aleutian-Yakutat slab subducts, similar to other subduction zones. This attenuation differential is observed in both the volcanic Cook Inlet segment and amagmatic Denali segments of the Aleutian subduction zone. By comparison, preliminary results for the Wrangell-St. Elias region past the eastern edge of the Aleutian slab show strong attenuation beneath the Wrangell Volcanic Field, as well as much further south than in the Cook Inlet-Kenai region. This pattern of attenuation seems to indicate a short slab fragment in the east of the subduction zone, though the picture is complex. Results also suggest the slab may focus or transmit energy with minimal attenuation, adding to the complexity. To image the critical transition between the Alaska-Aleutian slab and the region to its east, we plan to incorporate new broadband data from the WVLF array, an ongoing deployment of 37 PASSCAL instruments installed in 2016

  4. Preparation, characterization and millimetre wave attenuation performance of carbon fibers coated with nickel-wolfram-phosphorus and nickel-cobalt-wolfram- phosphorus

    International Nuclear Information System (INIS)

    Ye, Mingquan; Li, Zhitao; Wang, Chen; Han, Aijun

    2016-01-01

    Highlights: • SEM, XRD, EDS and MMW attenuation performances of alloys coated CFs were studied. • Resistivity and P content in alloys were main factors on MMW attenuation property. • The weight gain of coated CFs has effects on the MMW attenuation performance. - Abstract: Carbon fibers (CFs) coated with Ni–X–P (X = W, Co–W or none) alloys were prepared by electroless plating. The morphology, crystal structure, and element composition of alloy-coated CFs were characterized by scanning electron microscopy, X-ray diffractometry, energy-dispersive spectrometry and microwave attenuation. The results showed that CFs were coated with a layer of alloy particles. P content in Ni–Co–W–P or Ni–W–P alloys was lower than that in Ni–P alloy, and coating alloy Ni–P was amorphous. After W or Co introduction, coating alloys exhibited crystal characteristics. MMW-attenuation performance analysis showed that the 3 mm wave attenuation performance of CFs/Ni–Co–W–P, CFs/Ni–W–P and CFs/Ni–P increased by 7.27 dBm, 4.88 dBm and 3.55 dBm, and the 8 mm wave attenuation effects increased by 11.61 dBm, 6.11 dBm, and 4.06 dBm respectively, compared with those of CFs. MMW-attenuation performance is attributable to the sample bulk resistivity and P content in the alloy. Moreover, an optimal weight gain value existed for the MMW-attenuation performance of alloy-coated CFs.

  5. Insights into the attenuated sorption of organic compounds on black carbon aged in soil.

    Science.gov (United States)

    Luo, Lei; Lv, Jitao; Chen, Zien; Huang, Rixiang; Zhang, Shuzhen

    2017-12-01

    Sorption of organic compounds on fresh black carbons (BCs) can be greatly attenuated in soil over time. We examined herein the changes in surface properties of maize straw-derived BCs (biochars) after aged in a black soil and their effects on the sorptive behaviors of naphthalene, phenanthrene and 1,3-dinitrobenzene. Dissolved fulvic and humic acids extracted from the soil were used to explore the role of dissolved organic carbon (DOC) in the aging of biochars. Chromatography analysis indicated that DOC molecules with relatively large molecular weight were preferentially adsorbed on the biochars during the aging processes. DOC sorption led to blockage of the biochar's micropores according to N 2 and CO 2 adsorption analyses. Surface chemistry of the biochars was also substantially modified, with more O-rich functional groups on the aged biochars compared to the original biochars, as evidenced by Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses. The changes in both the physical and chemical surface properties of biochars by DOC led to significant attenuation of the sorption capacity and nonlinearity of the nonionic organic compounds on the aged biochars. Among the tested organic compounds, phenanthrene was the most attenuated in its sorption by the aging treatments, possibly because of its relatively large molecular size and hydrophobicity. The information can help gain a mechanistic understanding of interactions between BCs and organic compounds in soil environment. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Synergistic attenuation of myocardial fibrosis in spontaneously hypertensive rats by joint treatment with benazepril and candesartan.

    Science.gov (United States)

    Meng, Guoliang; Wu, Feng; Yang, Liyun; Zhu, Hongyan; Gu, Jinhua; He, Min; Xu, Jiliang

    2009-07-01

    Benazepril, an angiotensin-converting enzyme inhibitor, and candesartan, an angiotensin receptor blocker, are common drugs for treating hypertension. This study aimed to investigate the enhanced attenuation of myocardial fibrosis in spontaneously hypertensive rats (SHRs) possibly induced by joint treatment with benazepril and candesartan and the possible involvement of transforming growth factor beta1 (TGF-beta1)-Smad signaling pathway. SHRs were treated with benazepril at 10 mg.kg.d, candesartan at 4 mg.kg.d, and a combination of 2 drugs at half dose, respectively, for 12 weeks. Echocardiography and histology indicated that joint treatment with 2 drugs more significantly inhibited myocardial fibrosis in SHRs than either monotherapy, as evidenced by the changes in cardiac structural parameters, ultrasonic integrated backscatters, collagen volume fraction, and perivascular collagen area. The collagen analyses further revealed that significant decreases in total collagen concentration, the ratio of collagen type I to type III, and collagen cross-linking were found after the enhanced attenuation of myocardial fibrosis. Western blot analysis showed that the protein expression of TGF-beta1 and Smad3 was significantly decreased after joint treatment with 2 drugs. We conclude that synergistic attenuation of myocardial fibrosis in SHRs is produced by combined use of benazepril and candesartan possibly through the modulation of TGF-beta/Smad signaling proteins.

  7. 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

  8. Attenuation correction in emission tomography using the emission data—A review

    Energy Technology Data Exchange (ETDEWEB)

    Berker, Yannick, E-mail: berker@mail.med.upenn.edu; Li, Yusheng [Department of Radiology, University of Pennsylvania, 3620 Hamilton Walk, Philadelphia, Pennsylvania 19104 (United States)

    2016-02-15

    The problem of attenuation correction (AC) for quantitative positron emission tomography (PET) had been considered solved to a large extent after the commercial availability of devices combining PET with computed tomography (CT) in 2001; single photon emission computed tomography (SPECT) has seen a similar development. However, stimulated in particular by technical advances toward clinical systems combining PET and magnetic resonance imaging (MRI), research interest in alternative approaches for PET AC has grown substantially in the last years. In this comprehensive literature review, the authors first present theoretical results with relevance to simultaneous reconstruction of attenuation and activity. The authors then look back at the early history of this research area especially in PET; since this history is closely interwoven with that of similar approaches in SPECT, these will also be covered. We then review algorithmic advances in PET, including analytic and iterative algorithms. The analytic approaches are either based on the Helgason–Ludwig data consistency conditions of the Radon transform, or generalizations of John’s partial differential equation; with respect to iterative methods, we discuss maximum likelihood reconstruction of attenuation and activity (MLAA), the maximum likelihood attenuation correction factors (MLACF) algorithm, and their offspring. The description of methods is followed by a structured account of applications for simultaneous reconstruction techniques: this discussion covers organ-specific applications, applications specific to PET/MRI, applications using supplemental transmission information, and motion-aware applications. After briefly summarizing SPECT applications, we consider recent developments using emission data other than unscattered photons. In summary, developments using time-of-flight (TOF) PET emission data for AC have shown promising advances and open a wide range of applications. These techniques may both remedy

  9. Implementation of Enhanced Attenuation at the DOE Mound Site OU-1 Landfill: Accelerating Progress and Reducing Costs

    Energy Technology Data Exchange (ETDEWEB)

    Hooten, Gwendolyn [U.S. Department of Energy, Office of Legacy Management; Cato, Rebecca [Navarro Research and Engineering; Looney, Brian [Savannah River National Laboratory, Aiken, SC

    2016-03-06

    At the US Department of Energy (DOE), Office of Legacy Management, Mound, Ohio, Site, chlorinated organic contaminants (cVOCs) originating from the former solid-waste landfill have impacted groundwater in Operable Unit 1 (OU-1). The baseline groundwater remedy was groundwater pump and treat (P&T). Since the source materials have been removed from the landfill, the Mound core team, which consists of DOE, US Environmental Protection Agency (US EPA), Ohio EPA, and other stakeholders, is assessing the feasibility of switching from the active P&T remedy to a passive attenuation-based remedy. Toward this end, an enhanced attenuation (EA) strategy based on the creation of structured geochemical zones was developed. This EA strategy addresses the residual areas of elevated cVOCs in soil and groundwater while minimizing the rebound of groundwater concentrations above regulatory targets (e.g., maximum contaminant levels [MCLs]) and avoiding plume expansion while the P&T system is turned off. The EA strategy has improved confidence and reduced risk on the OU-1 groundwater transition path to monitored natural attenuation (MNA). To better evaluate the EA strategy, DOE is conducting a field demonstration to evaluate the use of edible oils to enhance the natural attenuation processes. The field demonstration is designed to determine whether structured geochemical zones can be established that expedite the attenuation of cVOCs in the OU-1 groundwater. The EA approach at OU-1 was designed based on “structured geochemical zones” and relies on groundwater flow through a succession of anaerobic and aerobic zones. The anaerobic zones stimulate relatively rapid degradation of the original solvent source compounds (e.g., cVOCs such as tetrachloroethene [PCE] and trichloroethene [TCE]). The surrounding aerobic areas encourage relatively rapid degradation of daughter products (such as dichloroethene [DCE] and vinyl chloride [VC]) as well as enhanced cometabolism of TCE resulting from

  10. Impact of attenuation correction strategies on the quantification of High Resolution Research Tomograph PET studies

    International Nuclear Information System (INIS)

    Velden, Floris H P van; Kloet, Reina W; Berckel, Bart N M van; Molthoff, Carla F M; Jong, Hugo W A M de; Lammertsma, Adriaan A; Boellaard, Ronald

    2008-01-01

    In this study, the quantitative accuracy of different attenuation correction strategies presently available for the High Resolution Research Tomograph (HRRT) was investigated. These attenuation correction methods differ in reconstruction and processing (segmentation) algorithms used for generating a μ-image from measured 2D transmission scans, an intermediate step in the generation of 3D attenuation correction factors. Available methods are maximum-a-posteriori reconstruction (MAP-TR), unweighted OSEM (UW-OSEM) and NEC-TR, which transforms sinogram values back to their noise equivalent counts (NEC) to restore Poisson distribution. All methods can be applied with or without μ-image segmentation. However, for MAP-TR a μ-histogram is a prior during reconstruction. All possible strategies were evaluated using phantoms of various sizes, simulating preclinical and clinical situations. Furthermore, effects of emission contamination of the transmission scan on the accuracy of various attenuation correction strategies were studied. Finally, the accuracy of various attenuation corrections strategies and its relative impact on the reconstructed activity concentration (AC) were evaluated using small animal and human brain studies. For small structures, MAP-TR with human brain priors showed smaller differences in μ-values for transmission scans with and without emission contamination (<8%) than the other methods (<26%). In addition, it showed best agreement with true AC (deviation <4.5%). A specific prior designed to take into account the presence of small animal fixation devices only very slightly improved AC precision to 4.3%. All methods scaled μ-values of a large homogeneous phantom to within 4% of the water peak, but MAP-TR provided most accurate AC after reconstruction. However, for clinical data MAP-TR using the default prior settings overestimated the thickness of the skull, resulting in overestimations of μ-values in regions near the skull and thus in incorrect

  11. 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.

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

    International Nuclear Information System (INIS)

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

    2004-01-01

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

  13. Amplifying and attenuating the coffee-ring effect in drying sessile nanofluid droplets

    Science.gov (United States)

    Crivoi, A.; Duan, Fei

    2013-04-01

    Experiments and simulations to promote or attenuate the “coffee-ring effect” for pinned sessile nanofluid droplets are presented. The addition of surfactant inside a water suspension of aluminum oxide nanoparticles results in coffee-ring formation after the pinned sessile droplets are fully dried on a substrate, while droplets of the same suspension without the surfactant produce a fine uniform coverage. A mathematical model based on diffusion-limited cluster-cluster aggregation has been developed to explain the observed difference in the experiments. The simulations show that the particle sticking probability is a crucial factor on the morphology of finally dried structures.

  14. Development of spectral shapes and attenuation relations from accelerograms recorded on rock and soil sites

    International Nuclear Information System (INIS)

    Ghosh, A.K.; Rao, K.S.; Kushwaha, H.S.

    1998-06-01

    Earthquake accelerograms recorded on rock and soil sites have been analysed. Site-specific response spectra and peak ground acceleration attenuation relations have been developed. This report presents the normalised pseudo-absolute acceleration spectra for various values of damping and for various confidence levels. Scaling laws have been developed for the response spectra. The present results are based on a large database and comparison has been made with earlier results. These results will be useful in the earthquake resistant design of structures. (author)

  15. Development of spectral shapes and attenuation relations from accelerograms recorded on rock and soil sites

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, A K; Rao, K S; Kushwaha, H S [Reactor Safety Div., Bhabha Atomic Research Centre, Mumbai (India)

    1998-06-01

    Earthquake accelerograms recorded on rock and soil sites have been analysed. Site-specific response spectra and peak ground acceleration attenuation relations have been developed. This report presents the normalised pseudo-absolute acceleration spectra for various values of damping and for various confidence levels. Scaling laws have been developed for the response spectra. The present results are based on a large database and comparison has been made with earlier results. These results will be useful in the earthquake resistant design of structures. (author) 22 refs., 7 figs., 5 tabs.

  16. 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

  17. 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

  18. 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)

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. 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

  4. 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.

  5. Integrated PET/MR breast cancer imaging: Attenuation correction and implementation of a 16-channel RF coil

    Energy Technology Data Exchange (ETDEWEB)

    Oehmigen, Mark, E-mail: mark.oehmigen@uni-due.de; Lindemann, Maike E. [High Field and Hybrid MR Imaging, University Hospital Essen, Essen 45147 (Germany); Lanz, Titus [Rapid Biomedical GmbH, Rimpar 97222 (Germany); Kinner, Sonja [Institute for Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen 45147 (Germany); Quick, Harald H. [High Field and Hybrid MR Imaging, University Hospital Essen, Essen 45147, Germany and Erwin L. Hahn Institute for MR Imaging, University Duisburg-Essen, Essen 45141 (Germany)

    2016-08-15

    Purpose: This study aims to develop, implement, and evaluate a 16-channel radiofrequency (RF) coil for integrated positron emission tomography/magnetic resonance (PET/MR) imaging of breast cancer. The RF coil is designed for optimized MR imaging performance and PET transparency and attenuation correction (AC) is applied for accurate PET quantification. Methods: A 16-channel breast array RF coil was designed for integrated PET/MR hybrid imaging of breast cancer lesions. The RF coil features a lightweight rigid design and is positioned with a spacer at a defined position on the patient table of an integrated PET/MR system. Attenuation correction is performed by generating and applying a dedicated 3D CT-based template attenuation map. Reposition accuracy of the RF coil on the system patient table while using the positioning frame was tested in repeated measurements using MR-visible markers. The MR, PET, and PET/MR imaging performances were systematically evaluated using modular breast phantoms. Attenuation correction of the RF coil was evaluated with difference measurements of the active breast phantoms filled with radiotracer in the PET detector with and without the RF coil in place, serving as a standard of reference measurement. The overall PET/MR imaging performance and PET quantification accuracy of the new 16-channel RF coil and its AC were then evaluated in first clinical examinations on ten patients with local breast cancer. Results: The RF breast array coil provides excellent signal-to-noise ratio and signal homogeneity across the volume of the breast phantoms in MR imaging and visualizes small structures in the phantoms down to 0.4 mm in plane. Difference measurements with PET revealed a global loss and thus attenuation of counts by 13% (mean value across the whole phantom volume) when the RF coil is placed in the PET detector. Local attenuation ranging from 0% in the middle of the phantoms up to 24% was detected in the peripheral regions of the phantoms at

  6. Attenuation correction method for single photon emission CT

    Energy Technology Data Exchange (ETDEWEB)

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

    1983-10-01

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

  7. Statistical modeling of optical attenuation measurements in continental fog conditions

    Science.gov (United States)

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

    2017-03-01

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

  8. 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.

  9. Iterative methods for photoacoustic tomography in attenuating acoustic media

    Science.gov (United States)

    Haltmeier, Markus; Kowar, Richard; Nguyen, Linh V.

    2017-11-01

    The development of efficient and accurate reconstruction methods is an important aspect of tomographic imaging. In this article, we address this issue for photoacoustic tomography. To this aim, we use models for acoustic wave propagation accounting for frequency dependent attenuation according to a wide class of attenuation laws that may include memory. We formulate the inverse problem of photoacoustic tomography in attenuating medium as an ill-posed operator equation in a Hilbert space framework that is tackled by iterative regularization methods. Our approach comes with a clear convergence analysis. For that purpose we derive explicit expressions for the adjoint problem that can efficiently be implemented. In contrast to time reversal, the employed adjoint wave equation is again damping and, thus has a stable solution. This stability property can be clearly seen in our numerical results. Moreover, the presented numerical results clearly demonstrate the efficiency and accuracy of the derived iterative reconstruction algorithms in various situations including the limited view case.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. Modeling of the attenuation of stress waves in concrete based on the Rayleigh damping model using time-reversal and PZT transducers

    Science.gov (United States)

    Tian, Zhen; Huo, Linsheng; Gao, Weihang; Li, Hongnan; Song, Gangbing

    2017-10-01

    Wave-based concrete structural health monitoring has attracted much attention. A stress wave experiences significant attenuation in concrete, however there is a lack of a unified method for predicting the attenuation coefficient of the stress wave. In this paper, a simple and effective absorption attenuation model of stress waves in concrete is developed based on the Rayleigh damping model, which indicates that the absorption attenuation coefficient of stress waves in concrete is directly proportional to the square of the stress wave frequency when the damping ratio is small. In order to verify the theoretical model, related experiments were carried out. During the experiments, a concrete beam was designed in which the d33-model piezoelectric smart aggregates were embedded to detect the propagation of stress waves. It is difficult to distinguish direct stress waves due to the complex propagation paths and the reflection and scattering of stress waves in concrete. Hence, as another innovation of this paper, a new method for computing the absorption attenuation coefficient based on the time-reversal method is developed. Due to the self-adaptive focusing properties of the time-reversal method, the time-reversed stress wave focuses and generates a peak value. The time-reversal method eliminates the adverse effects of multipaths, reflection, and scattering. The absorption attenuation coefficient is computed by analyzing the peak value changes of the time-reversal focused signal. Finally, the experimental results are found to be in good agreement with the theoretical model.

  16. Attenuation of Foot-and-Mouth Disease Virus by Engineered Viral Polymerase Fidelity.

    Science.gov (United States)

    Rai, Devendra K; Diaz-San Segundo, Fayna; Campagnola, Grace; Keith, Anna; Schafer, Elizabeth A; Kloc, Anna; de Los Santos, Teresa; Peersen, Olve; Rieder, Elizabeth

    2017-08-01

    Foot-and-mouth disease virus (FMDV) RNA-dependent RNA polymerase (RdRp) (3D pol ) catalyzes viral RNA synthesis. Its characteristic low fidelity and absence of proofreading activity allow FMDV to rapidly mutate and adapt to dynamic environments. In this study, we used the structure of FMDV 3D pol in combination with previously reported results from similar picornaviral polymerases to design point mutations that would alter replication fidelity. In particular, we targeted Trp237 within conserved polymerase motif A because of the low reversion potential inherent in the single UGG codon. Using biochemical and genetic tools, we show that the replacement of tryptophan 237 with phenylalanine imparts higher fidelity, but replacements with isoleucine and leucine resulted in lower-fidelity phenotypes. Viruses containing these W237 substitutions show in vitro growth kinetics and plaque morphologies similar to those of the wild-type (WT) A 24 Cruzeiro strain in BHK cells, and both high- and low-fidelity variants retained fitness during coinfection with the wild-type virus. The higher-fidelity W237F (W237F HF ) mutant virus was more resistant to the mutagenic nucleoside analogs ribavirin and 5-fluorouracil than the WT virus, whereas the lower-fidelity W237I (W237I LF ) and W237L LF mutant viruses exhibited lower ribavirin resistance. Interestingly, the variant viruses showed heterogeneous and slightly delayed growth kinetics in primary porcine kidney cells, and they were significantly attenuated in mouse infection experiments. These data demonstrate, for a single virus, that either increased or decreased RdRp fidelity attenuates virus growth in animals, which is a desirable feature for the development of safer and genetically more stable vaccine candidates. IMPORTANCE Foot-and-mouth disease (FMD) is the most devastating disease affecting livestock worldwide. Here, using structural and biochemical analyses, we have identified FMDV 3D pol mutations that affect polymerase

  17. Seismic attenuation in the African LLSVP estimated from PcS phases

    Science.gov (United States)

    Liu, Chujie; Grand, Stephen P.

    2018-05-01

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

  18. Note: Attenuation motion of acoustically levitated spherical rotor

    Science.gov (United States)

    Lü, P.; Hong, Z. Y.; Yin, J. F.; Yan, N.; Zhai, W.; Wang, H. P.

    2016-11-01

    Here we observe the attenuation motion of spherical rotors levitated by near-field acoustic radiation force and analyze the factors that affect the duration time of free rotation. It is found that the rotating speed of freely rotating rotor decreases exponentially with respect to time. The time constant of exponential attenuation motion depends mainly on the levitation height, the mass of rotor, and the depth of concave ultrasound emitter. Large levitation height, large mass of rotor, and small depth of concave emitter are beneficial to increase the time constant and hence extend the duration time of free rotation.

  19. 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)

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

    International Nuclear Information System (INIS)

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

    1986-01-01

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

  1. Prediction of slant path rain attenuation statistics at various locations

    Science.gov (United States)

    Goldhirsh, J.

    1977-01-01

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

  2. 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)

  3. 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

  4. Continental Fog Attenuation Empirical Relationship from Measured Visibility Data

    Directory of Open Access Journals (Sweden)

    F. Nadeem

    2010-12-01

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

  5. Evaluation of X ray attenuation by means of radiographic images

    International Nuclear Information System (INIS)

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

    2011-01-01

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

  6. Signal attenuation due to cavity leakage

    International Nuclear Information System (INIS)

    Sherman, M.H.; Modera, M.P.

    1988-01-01

    The propagation of sound waves in fluids requires information about three properties of the system: capacitance (compressibility), resistance (friction), and inductance (inertia). Acoustical design techniques to date have tended to ignore the frictional effects associated with airflow across the envelope of the acoustic cavity (e.g., resistive vents). Since such leakage through the cavity envelope is best expressed with a power law dependence on the pressure, standard Fourier techniques that rely on linearity cannot be used. In this article, the theory relevant to nonlinear leakage is developed and equations presented. Potential applications of the theory to techniques for quantifying the leakage of buildings are presented. Experimental results from pressure decays in a full-scale test structure are presented and the leakage so measured is compared with independent measurements to demonstrate the technique

  7. Vaccinia virus recombinants expressing chimeric proteins of human immunodeficiency virus and gamma interferon are attenuated for nude mice.

    OpenAIRE

    Giavedoni, L D; Jones, L; Gardner, M B; Gibson, H L; Ng, C T; Barr, P J; Yilma, T

    1992-01-01

    We have developed a method for attenuating vaccinia virus recombinants by expressing a fusion protein of a lymphokine and an immunogen. Chimeric genes were constructed that coded for gamma interferon (IFN-gamma) and structural proteins of the human immunodeficiency virus type 1 (HIV-1). In this study, we describe the biological and immunological properties of vaccinia virus recombinants expressing chimeric genes of murine or human IFN-gamma with glycoprotein gp120, gag, and a fragment of gp41...

  8. Seismic moment tensors of acoustic emissions recorded during laboratory rock deformation experiments: sensitivity to attenuation and anisotropy

    Czech Academy of Sciences Publication Activity Database

    Stierle, E.; Vavryčuk, Václav; Kwiatek, G.; Charalampidou, E.-M.; Bohnhoff, M.

    2016-01-01

    Roč. 205, č. 1 (2016), s. 38-50 ISSN 0956-540X R&D Projects: GA ČR(CZ) GAP210/12/1491; GA ČR(CZ) GC16-19751J Institutional support: RVO:67985530 Keywords : earthquake source observations * seismic anisotropy * seismic attenuation * wave propagation * acoustic properties Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 2.414, year: 2016

  9. Structural and electronic properties of boron-doped double-walled silicon carbide nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Behzad, Somayeh, E-mail: somayeh.behzad@gmail.co [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of); Moradian, Rostam [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of); Nano Science and Technology Research Center, Razi University, Kermanshah (Iran, Islamic Republic of); Computational Physical Science Research Laboratory, Department of Nano Science, Institute for Studies in Theoretical Physics and Mathematics (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Chegel, Raad [Physics Department, Faculty of Science, Razi University, Kermanshah (Iran, Islamic Republic of)

    2010-12-01

    The effects of boron doping on the structural and electronic properties of (6,0)-(14,0) double-walled silicon carbide nanotube (DWSiCNT) are investigated by using spin-polarized density functional theory. It is found that boron atom could be more easily doped in the inner tube. Our calculations indicate that a Si site is favorable for B under C-rich condition and a C site is favorable under Si-rich condition. Additionally, B-substitution at either single carbon or silicon atom site in DWSiCNT could induce spontaneous magnetization.

  10. Structural and electronic properties of boron-doped double-walled silicon carbide nanotubes

    International Nuclear Information System (INIS)

    Behzad, Somayeh; Moradian, Rostam; Chegel, Raad

    2010-01-01

    The effects of boron doping on the structural and electronic properties of (6,0)-(14,0) double-walled silicon carbide nanotube (DWSiCNT) are investigated by using spin-polarized density functional theory. It is found that boron atom could be more easily doped in the inner tube. Our calculations indicate that a Si site is favorable for B under C-rich condition and a C site is favorable under Si-rich condition. Additionally, B-substitution at either single carbon or silicon atom site in DWSiCNT could induce spontaneous magnetization.

  11. Structural and electronic properties of boron-doped double-walled silicon carbide nanotubes

    Science.gov (United States)

    Behzad, Somayeh; Moradian, Rostam; Chegel, Raad

    2010-12-01

    The effects of boron doping on the structural and electronic properties of (6,0)@(14,0) double-walled silicon carbide nanotube (DWSiCNT) are investigated by using spin-polarized density functional theory. It is found that boron atom could be more easily doped in the inner tube. Our calculations indicate that a Si site is favorable for B under C-rich condition and a C site is favorable under Si-rich condition. Additionally, B-substitution at either single carbon or silicon atom site in DWSiCNT could induce spontaneous magnetization.

  12. 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.

  13. Beam Attenuators and the Risk of Unrecognized Large-Fraction Irradiation of Critical Tissues

    International Nuclear Information System (INIS)

    Luka, S.; Marks, J.E.

    2015-01-01

    The use of radiation beam attenuators led to radiation injury of the spinal cord in one patient and of the peripheral nerve in another due to unsuspected large-fraction irradiation. The anatomic distribution of radiation dose was reconstructed in the sagittal plane for the patient who developed radiation myelopathy and in the axial plane for the patient who developed peripheral neuropathy. The actual dose delivered to the injured structure in each patient was taken from the dose distribution and recorded along with the time, number of fractions, and dose per fraction. The patient who developed radiation myelopathy received a total of 46.5 Gy in twenty-three 2.1 Gy fractions in 31 days to the upper cervical spinal cord where the thickness of the neck was less than the central axis thickness due to cervical lordosis and absence of a posterior compensating filter. The patient who developed peripheral neuropathy received 55 Gy in twenty-five 2.2 Gy fractions in 50 days to the femoral nerve using bolus over the groins and an anterior one-half value layer Cerrobend pelvic block to bias the dose anteriorly. Compensating filters and other beam attenuators should be used with caution because they may result in unsuspected large-fraction irradiation and total doses of radiation that exceed the tolerance of critical structures.

  14. Beam Attenuators and the Risk of Unrecognized Large-Fraction Irradiation of Critical Tissues

    Energy Technology Data Exchange (ETDEWEB)

    Luka, S.; Marks, J.E.

    2015-01-15

    The use of radiation beam attenuators led to radiation injury of the spinal cord in one patient and of the peripheral nerve in another due to unsuspected large-fraction irradiation. The anatomic distribution of radiation dose was reconstructed in the sagittal plane for the patient who developed radiation myelopathy and in the axial plane for the patient who developed peripheral neuropathy. The actual dose delivered to the injured structure in each patient was taken from the dose distribution and recorded along with the time, number of fractions, and dose per fraction. The patient who developed radiation myelopathy received a total of 46.5 Gy in twenty-three 2.1 Gy fractions in 31 days to the upper cervical spinal cord where the thickness of the neck was less than the central axis thickness due to cervical lordosis and absence of a posterior compensating filter. The patient who developed peripheral neuropathy received 55 Gy in twenty-five 2.2 Gy fractions in 50 days to the femoral nerve using bolus over the groins and an anterior one-half value layer Cerrobend pelvic block to bias the dose anteriorly. Compensating filters and other beam attenuators should be used with caution because they may result in unsuspected large-fraction irradiation and total doses of radiation that exceed the tolerance of critical structures.

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

    Science.gov (United States)

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

    2015-11-01

    The neurosteroid dehydroepiandrosterone (DHEA) is involved in the pathophysiology of several psychiatric disorders, including cocaine addiction. We have previously shown that DHEA attenuates cocaine-seeking behaviour, and also that DHEA decreases corticosterone (CORT) levels in plasma and the prefrontal cortex. Previous studies have found that rats demonstrate cocaine-seeking behaviour only when the level of CORT reaches a minimum threshold. In the present study, we investigated whether the attenuating effect of DHEA on cocaine seeking is a result of it reducing CORT levels rather than a result of any unique neurosteroid properties. Rats received either daily DHEA injections (2 mg/kg, i.p.) alone, daily DHEA (2 mg/kg, i.p.) with CORT infusion (to maintain stable basal levels of CORT; 15 mg/kg, s.c.) or vehicle (i.p.) as control, throughout self-administration training and extinction sessions. We found that both DHEA-treated and DHEA + CORT-treated groups showed a significantly lower number of active lever presses compared to controls throughout training and extinction sessions, as well as at cocaine-primed reinstatement. DHEA-treated rats showed lower CORT levels throughout the experimental phases compared to DHEA + CORT-treated and control rats. Additionally, we show that DHEA administered to cocaine-trained rats throughout extinction sessions, or immediately before reinstatement, attenuated cocaine seeking. These findings indicate that DHEA attenuates cocaine-seeking behaviour independently of fluctuations in CORT levels. © 2015 British Society for Neuroendocrinology.

  16. Photosynthetic efficiency of Chlamydomonas reinhardtii in attenuated, flashing light

    NARCIS (Netherlands)

    Vejrazka, C.; Janssen, M.G.J.; Streefland, M.; Wijffels, R.H.

    2012-01-01

    As a result of mixing and light attenuation, algae in a photobioreactor (PBR) alternate between light and dark zones and, therefore, experience variations in photon flux density (PFD). These variations in PFD are called light/dark (L/D) cycles. The objective of this study was to determine how these

  17. Ixeris dentata (Thunb) Nakai attenuates cognitive impairment in ...

    African Journals Online (AJOL)

    Ixeris dentata (Thunb) Nakai attenuates cognitive impairment in MPTP-treated mouse model of Parkinson's disease. ... Conclusion: IDE exhibits good protection against MPTP-induced behavioral deficits via potential antioxidant defense mechanisms. Therefore, IDE could potentially be developed as a therapeutic approach ...

  18. Oral vaccination with attenuated Salmonella choleraesuis C500 ...

    African Journals Online (AJOL)

    user

    Marshall, 1983), and well known as the major gastro- duodenal ... The CagA is encoded in a pathogenicity island known as 'Cag PAI' and is .... HindIII to release the CagA fragment. The purified .... vaccine strain attenuated by chemical methods, which is .... pylori antigens is achieved using a non-toxic mutant of E. coli heat-.

  19. NATURAL ATTENUATION OF COPPER IN SOILS AND SOIL MINERALS - II

    Science.gov (United States)

    The bioabailability and toxicity of Cu in soils is controlled by a number of soil properties and processes. Some of these such as pH, adsorption/desorption and competition with beneficial cations have been extensively studied. However, the effects of natural attenuation (or aging...

  20. Context discovery using attenuated Bloom codes: model description and validation

    NARCIS (Netherlands)

    Liu, F.; Heijenk, Geert

    A novel approach to performing context discovery in ad-hoc networks based on the use of attenuated Bloom filters is proposed in this report. In order to investigate the performance of this approach, a model has been developed. This document describes the model and its validation. The model has been

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

    African Journals Online (AJOL)

    ADOWIE PERE

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

  2. Comparison of Attenuation of petroleum hydrocarbons in surface ...

    African Journals Online (AJOL)

    These concentrations further changed at day 56 with the non amended soils now having the lowest TPH concentrations. 56 days after spiking with TPH, only the C 10 – C 12 and > C16 carbon number fractions were detected at both depths. Results suggest that natural attenuation can be a viable remediation strategy in ...

  3. 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.

  4. 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)

  5. Chemical oxygen demand (cod) attenuation of methyl red in water ...

    African Journals Online (AJOL)

    Chemical oxygen demand (cod) attenuation of methyl red in water using biocarbons obtained from Nipa palm leaves. ... eco-friendly and locally accessible biocarbon for mitigation of organic contaminants in water. Keywords: Chemical oxygen demand, biocarbon, methyl red, biodegradation, bioremediation, Nipa palm ...

  6. Variable optical attenuator fabricated by direct UV writing

    DEFF Research Database (Denmark)

    Svalgaard, Mikael; Færch, Kjartan Ullitz; Andersen, L.U.

    2003-01-01

    It is demonstrated that direct ultraviolet writing of waveguides is a method suitable for mass production of compact variable optical attenuators with low insertion loss, low polarization-dependent loss, and high dynamic range. The fabrication setup is shown to be robust, providing good device...

  7. Wave attenuation model for dephasing and measurement of ...

    Indian Academy of Sciences (India)

    An analysis of previous models to simulate inelastic scattering in such systems is presented and a relatively new model based on wave attenuation is introduced. The problem of Aharonov–Bohm (AB) oscillations in conductance of a mesoscopic ring is studied. We show that the conductance is symmetric under flux reversal ...

  8. Timing attention : Cuing target onset interval attenuates the attentional blink

    NARCIS (Netherlands)

    Martens, S; Johnson, A

    Three experiments tested whether the attentional blink (AB; a deficit in reporting the second of two targets when it occurs 200-500 msec after the first) can be attenuated by providing information about the target onset asynchrony (TOA) of the second target relative to the first. Blocking the TOA

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

    NARCIS (Netherlands)

    Koelmans, A.A.; Meulman, B.; Meijer, T.; Jonker, M.T.O.

    2009-01-01

    Strong sorption to black carbon may limit the environmental risks of organic pollutants, but interactions with cosorbing humic acid (HA) may interfere. We studied the attenuative effect of HA additions on the sorption of polychlorinated biphenyls (PCBs) to a charcoal. "Intrinsic" sorption to

  10. Seismic noise attenuation using an online subspace tracking algorithm

    NARCIS (Netherlands)

    Zhou, Yatong; Li, Shuhua; Zhang, D.; Chen, Yangkang

    2018-01-01

    We propose a new low-rank based noise attenuation method using an efficient algorithm for tracking subspaces from highly corrupted seismic observations. The subspace tracking algorithm requires only basic linear algebraic manipulations. The algorithm is derived by analysing incremental gradient

  11. 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.

  12. Attenuation studies near K-absorption edges using Compton ...

    Indian Academy of Sciences (India)

    The results are consistent with theoretical values derived from the XCOM package. Keywords. Photon interaction; 241Am; gamma ray attenuation; Compton scattering; absorption edge; rare earth elements. PACS Nos 32.80.-t; 32.90.+a. 1. Introduction. Photon interaction studies at energies around the absorption edge have ...

  13. On self-attenuation corrections in gamma-ray spectrometry

    International Nuclear Information System (INIS)

    Bolivar, J.P.; Garcia-Leon, M.; Garcia-Tenorio, R.

    1997-01-01

    In this paper we discuss and justify the dependence on the sample density and gamma energy of the self-attenuation correction factor, f, in the transmission method for the full energy peak efficiency calibration of Ge detectors. It is suggested as a method for the direct computing of f in the case that the sample composition is known. (Author)

  14. Outdoor FSO Communications Under Fog: Attenuation Modeling and Performance Evaluation

    KAUST Repository

    Esmail, Maged Abdullah

    2016-07-18

    Fog is considered to be a primary challenge for free space optics (FSO) systems. It may cause attenuation that is up to hundreds of decibels per kilometer. Hence, accurate modeling of fog attenuation will help telecommunication operators to engineer and appropriately manage their networks. In this paper, we examine fog measurement data coming from several locations in Europe and the United States and derive a unified channel attenuation model. Compared with existing attenuation models, our proposed model achieves a minimum of 9 dB, which is lower than the average root-mean-square error (RMSE). Moreover, we have investigated the statistical behavior of the channel and developed a probabilistic model under stochastic fog conditions. Furthermore, we studied the performance of the FSO system addressing various performance metrics, including signal-to-noise ratio (SNR), bit-error rate (BER), and channel capacity. Our results show that in communication environments with frequent fog, FSO is typically a short-range data transmission technology. Therefore, FSO will have its preferred market segment in future wireless fifth-generation/sixth-generation (5G/6G) networks having cell sizes that are lower than a 1-km diameter. Moreover, the results of our modeling and analysis can be applied in determining the switching/thresholding conditions in highly reliable hybrid FSO/radio-frequency (RF) networks.

  15. 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.

  16. Selection of gonadotrophin surge attenuating factor phage antibodies by bioassay.

    Science.gov (United States)

    Sorsa-Leslie, Tarja; Mason, Helen D; Harris, William J; Fowler, Paul A

    2005-09-26

    We aimed to combine the generation of "artificial" antibodies with a rat pituitary bioassay as a new strategy to overcome 20 years of difficulties in the purification of gonadotrophin surge-attenuating factor (GnSAF). A synthetic single-chain antibody (Tomlinson J) phage display library was bio-panned with partially purified GnSAF produced by cultured human granulosa/luteal cells. The initial screening with a simple binding immunoassay resulted in 8 clones that were further screened using our in-vitro rat monolayer bioassay for GnSAF. Initially the antibodies were screened as pooled phage forms and subsequently as individual, soluble, single-chain antibody (scAbs) forms. Then, in order to improve the stability of the scAbs for immunopurification purposes, and to widen the range of labelled secondary antibodies available, these were engineered into full-length human immunoglobulins. The immunoglobulin with the highest affinity for GnSAF and a previously described rat anti-GnSAF polyclonal antiserum was then used to immunopurify bioactive GnSAF protein. The two purified preparations were electrophoresed on 1-D gels and on 7 cm 2-D gels (pH 4-7). The candidate GnSAF protein bands and spots were then excised for peptide mass mapping. Three of the scAbs recognised GnSAF bioactivity and subsequently one clone of the purified scAb-derived immunoglobulin demonstrated high affinity for GnSAF bioactivity, also binding the molecule in such as way as to block its bioactivity. When used for repeated immunopurification cycles and then Western blot, this antibody enabled the isolation of a GnSAF-bioactive protein band at around 66 kDa. Similar results were achieved using the rat anti-GnSAF polyclonal antiserum. The main candidate molecules identified from the immunopurified material by excision of 2-D gel protein spots was human serum albumin precursor and variants. This study demonstrates that the combination of bioassay and phage display technologies is a powerful tool in the

  17. 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

  18. 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

  19. 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.

  20. DETERMINATION OF ATTENUATION INDEX CURVE "Ri(f" FOR HOMOGENEOUS DOUBLE LOCKING ELEMENTS

    Directory of Open Access Journals (Sweden)

    BUZATU G. C.

    2016-12-01

    Full Text Available The paper is structured in three parts. In the first part of the paper, are presented some theoretical notions regarding the sound, noise, the sound insulations materials. Also in the first part of the paper are presented some characteristic regarding the insulation materials and there effects. In the second part it is described an calculation example for a homogeneous wall with double structure in order to determine the attenuation index curve "Ri(f". The example calculation contains 10 steps that must be followed and the final results are presented in table 7 and figure 3. The last part of the paper is represented by conclusions, where the authors tried to explain the importance of the curve "Ri(f" for reducing the noise in the buildings.

  1. Molecular recognition of pyr mRNA by the Bacillus subtilis attenuation regulatory protein PyrR

    Science.gov (United States)

    Bonner, Eric R.; D’Elia, John N.; Billips, Benjamin K.; Switzer, Robert L.

    2001-01-01

    The pyrimidine nucleotide biosynthesis (pyr) operon in Bacillus subtilis is regulated by transcriptional attenuation. The PyrR protein binds in a uridine nucleotide-dependent manner to three attenuation sites at the 5′-end of pyr mRNA. PyrR binds an RNA-binding loop, allowing a terminator hairpin to form and repressing the downstream genes. The binding of PyrR to defined RNA molecules was characterized by a gel mobility shift assay. Titration indicated that PyrR binds RNA in an equimolar ratio. PyrR bound more tightly to the binding loops from the second (BL2 RNA) and third (BL3 RNA) attenuation sites than to the binding loop from the first (BL1 RNA) attenuation site. PyrR bound BL2 RNA 4–5-fold tighter in the presence of saturating UMP or UDP and 150- fold tighter with saturating UTP, suggesting that UTP is the more important co-regulator. The minimal RNA that bound tightly to PyrR was 28 nt long. Thirty-one structural variants of BL2 RNA were tested for PyrR binding affinity. Two highly conserved regions of the RNA, the terminal loop and top of the upper stem and a purine-rich internal bulge and the base pairs below it, were crucial for tight binding. Conserved elements of RNA secondary structure were also required for tight binding. PyrR protected conserved areas of the binding loop in hydroxyl radical footprinting experiments. PyrR likely recognizes conserved RNA sequences, but only if they are properly positioned in the correct secondary structure. PMID:11726695

  2. A study on CT attenuation and MR signal intensity of protein solution

    International Nuclear Information System (INIS)

    Kim, Joung Hae; Choi, Dae Seob; Kim, Soon; Lee, Hyeon Kyeong; Oh, Hyeon Hee; Kim, Seung Hyeon; Lee, Sung Woo; Chang, Kee Hyun; Chung, Jun Ho

    2001-01-01

    To correlate CT attenuation and MR signal intensity with concentration of protein solution. CT and MR examinations of a phantom containing bovine serum albumin solutions of various concentrations ranging from 0 to 55% were performed. CT Hounsfield units(HUs), MR signal intensities, and apparent diffusion coefficients (ADCs) of each albumin solution were measured, and CT HUs and MR signal intensities of the solutions were compared with those of cerebrospinal fluid (CSF), white matter, and cortical gray matter. CT HU increased gradually with increasing albumin concentration. On T1-weighted images(T1WI), signal intensity increased with increasing albumin concentrations of up to 35% but then decreased. On T2-weighted images(T2Wl), gradually decreasing signal intensity and increasing albumin concentration were observed Fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted images (DWls) showed that signal intensity peaked at a concentration of 10% and then gradually decreased. The ADC of the solution gradually decreased as concentration increased. Compared with those of normal brain structures, the CT HUs of solutions at concentrations of over 20% were higher than those of white and gray matter. At T1WI, the signal intensities of 10-45% solutions were similar to or higher than that of the gray matter. At T2Wl, the signal intensities of solutions above 25, 35, and 40% were lower than those of CSF, gray matter, and white matter, respectively. FLAIR images showed that the signal intensities of 5-35% solutions were higher than that of gray matter. The CT attenuation of albumin solution increased gradually with increasing concentration. MR signal intensities peaked at 35% concentration on T1WI and at 10% on FLAIR and DW images, respectively, and then gradually decreased. T2Wl and ADC map images showed gradually decreasing signal intensity and ADC as albumin concentration increased

  3. Estimation of viscoelastic attenuation of real seismic data by use of ray tracing software: Application to the detection of gas hydrates and free gas

    Czech Academy of Sciences Publication Activity Database

    Bouchaala, Fateh; Guennou, C.

    2012-01-01

    Roč. 344, č. 2 (2012), s. 57-66 ISSN 1631-0713 Institutional research plan: CEZ:AV0Z30120515 Keywords : viscoelastic attenuation * gas hydrates * free gas * ray tracing Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.401, year: 2012

  4. 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

  5. Viscothermal Coupling Effects on Sound Attenuation in Concentrated Colloidal Dispersions.

    Science.gov (United States)

    Han, Wei

    1995-11-01

    This thesis describes a Unified Coupled Phase Continuum (UCPC) model to analyze sound propagation through aerosols, emulsions and suspensions in terms of frequency dependent attenuation coefficient and sound speed. Expressions for the viscous and thermal coupling coefficients explicitly account for the effects of particle size, shape factor, orientation as well as concentration and the sound frequency. The UCPC model also takes into account the intrinsic acoustic absorption within the fluid medium due to its viscosity and heat conductivity. The effective complex wave number as a function of frequency is derived. A frequency- and concentration-dependent complex Nusselt number for the interfacial thermal coupling coefficient is derived using an approximate similarity between the 'viscous skin drag' and 'heat conduction flux' associated with the discontinuous suspended phase, on the basis of a cell model. The theoretical predictions of attenuation spectra provide satisfactory agreement with reported experimental data on two concentrated suspensions (polystyrene latex and kaolin pigment), two concentrated emulsions (toluene -in-water, n-hexadecane-in-water), and two aerosols (oleic acid droplets-in-nitrogen, alumina-in-air), covering a wide range of relative magnitudes (from 10^ {-3} to 10^{3}) of thermal versus viscous contributions, for dispersed phase volume fractions as high as 50%. The relative differences between the additive result of separate viscous and thermal loss estimates and combined viscothermal absorption results are also presented. Effects of particle shape on viscous attenuation of sound in concentrated suspensions of non-spherical clay particles are studied. Attenuation spectra for 18 frequencies from 3 to 100 MHz are measured and analyzed for eleven kaolin clay slurries with solid concentrations ranging from 0.6% to 35% (w/w). A modified viscous drag coefficient that considers frequency, concentration, particle size, shape and orientation of

  6. 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

  7. 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

  8. Modeled Radar Attenuation Rate Profile at the Vostok 5G Ice Core Site, Antarctica, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides a modeled radar attenuation rate profile, showing the predicted contributions from pure ice and impurities to radar attenuation at the Vostok...

  9. Optimization of coronary optical coherence tomography imaging using the attenuation-compensated technique: a validation study.

    NARCIS (Netherlands)

    Teo, Jing Chun; Foin, Nicolas; Otsuka, Fumiyuki; Bulluck, Heerajnarain; Fam, Jiang Ming; Wong, Philip; Low, Fatt Hoe; Leo, Hwa Liang; Mari, Jean-Martial; Joner, Michael; Girard, Michael J A; Virmani, Renu; Bezerra, HG.; Costa, MA.; Guagliumi, G.; Rollins, AM.; Simon, D.; Gutiérrez-Chico, JL.; Alegría-Barrero, E.; Teijeiro-Mestre, R.; Chan, PH.; Tsujioka, H.; de Silva, R.; Otsuka, F.; Joner, M.; Prati, F.; Virmani, R.; Narula, J.; Members, WC.; Levine, GN.; Bates, ER.; Blankenship, JC.; Bailey, SR.; Bittl, JA.; Prati, F.; Guagliumi, G.; Mintz, G.S.; Costa, Marco; Regar, E.; Akasaka, T.; Roleder, T.; Jąkała, J.; Kałuża, GL.; Partyka, Ł.; Proniewska, K.; Pociask, E.; Girard, MJA.; Strouthidis, NG.; Ethier, CR.; Mari, JM.; Mari, JM.; Strouthidis, NG.; Park, SC.; Girard, MJA.; van der Lee, R.; Foin, N.; Otsuka, F.; Wong, P.K.; Mari, J-M.; Joner, M.; Nakano, M.; Vorpahl, M.; Otsuka, F.; Taniwaki, M.; Yazdani, SK.; Finn, AV.; Nakano, M.; Yahagi, K.; Yamamoto, H.; Taniwaki, M.; Otsuka, F.; Ladich, ER.; Girard, MJ.; Ang, M.; Chung, CW.; Farook, M.; Strouthidis, N.; Mehta, JS.; Foin, N.; Mari, JM.; Nijjer, S.; Sen, S.; Petraco, R.; Ghione, M.; Liu, X.; Kang, JU.; Virmani, R.; Kolodgie, F.D.; Burke, AP.; Farb, A.; Schwartz, S.M.; Yahagi, K.; Kolodgie, F.D.; Otsuka, F.; Finn, AV.; Davis, HR.; Joner, M.; Kume, T.; Akasaka, T.; Kawamoto, T.; Watanabe, N.; Toyota, E.; Neishi, Y.; Rieber, J.; Meissner, O.; Babaryka, G.; Reim, S.; Oswald, M.E.; Koenig, A.S.; Tearney, G. J.; Regar, E.; Akasaka, T.; Adriaenssens, T.; Barlis, P.; Bezerra, HG.; Yabushita, H.; Bouma, BE.; Houser, S. L.; Aretz, HT.; Jang, I-K.; Schlendorf, KH.; Guo, J.; Sun, L.; Chen, Y.D.; Tian, F.; Liu, HB.; Chen, L.; Kawasaki, M.; Bouma, BE.; Bressner, J. E.; Houser, S. L.; Nadkarni, S. K.; MacNeill, BD.; Jansen, CHP.; Onthank, DC.; Cuello, F.; Botnar, RM.; Wiethoff, AJ.; Warley, A.; von Birgelen, C.; Hartmann, A. M.; Kubo, T.; Akasaka, T.; Shite, J.; Suzuki, T.; Uemura, S.; Yu, B.; Habara, M.; Nasu, K.; Terashima, M.; Kaneda, H.; Yokota, D.; Ko, E.; Virmani, R.; Burke, AP.; Kolodgie, F.D.; Farb, A.; Takarada, S.; Imanishi, T.; Kubo, T.; Tanimoto, T.; Kitabata, H.; Nakamura, N.; Hattori, K.; Ozaki, Y.; Ismail, TF.; Okumura, M.; Naruse, H.; Kan, S.; Nishio, R.; Shinke, T.; Otake, H.; Nakagawa, M.; Nagoshi, R.; Inoue, T.; Sinclair, H.D.; Bourantas, C.; Bagnall, A.; Mintz, G.S.; Kunadian, V.; Tearney, G. J.; Yabushita, H.; Houser, S. L.; Aretz, HT.; Jang, I-K.; Schlendorf, KH.; van Soest, G.; Goderie, T.; Regar, E.; Koljenović, S.; Leenders, GL. van; Gonzalo, N.; Xu, C.; Schmitt, JM.; Carlier, SG.; Virmani, R.; van der Meer, FJ; Faber, D.J.; Sassoon, DMB.; Aalders, M.C.; Pasterkamp, G.; Leeuwen, TG. van; Schmitt, JM.; Knuttel, A.; Yadlowsky, M.; Eckhaus, MA.; Karamata, B.; Laubscher, M.; Leutenegger, M.; Bourquin, S.; Lasser, T.; Lambelet, P.; Vermeer, K.A.; Mo, J.; Weda, J.J.A.; Lemij, H.G.; Boer, JF. de

    2016-01-01

    PURPOSE To optimize conventional coronary optical coherence tomography (OCT) images using the attenuation-compensated technique to improve identification of plaques and the external elastic lamina (EEL) contour. METHOD The attenuation-compensated technique was optimized via manipulating contrast

  10. Modelling the attenuation in the ATHENA finite elements code for the ultrasonic testing of austenitic stainless steel welds.

    Science.gov (United States)

    Chassignole, B; Duwig, V; Ploix, M-A; Guy, P; El Guerjouma, R

    2009-12-01

    Multipass welds made in austenitic stainless steel, in the primary circuit of nuclear power plants with pressurized water reactors, are characterized by an anisotropic and heterogeneous structure that disturbs the ultrasonic propagation and makes ultrasonic non-destructive testing difficult. The ATHENA 2D finite element simulation code was developed to help understand the various physical phenomena at play. In this paper, we shall describe the attenuation model implemented in this code to give an account of wave scattering phenomenon through polycrystalline materials. This model is in particular based on the optimization of two tensors that characterize this material on the basis of experimental values of ultrasonic velocities attenuation coefficients. Three experimental configurations, two of which are representative of the industrial welds assessment case, are studied in view of validating the model through comparison with the simulation results. We shall thus provide a quantitative proof that taking into account the attenuation in the ATHENA code dramatically improves the results in terms of the amplitude of the echoes. The association of the code and detailed characterization of a weld's structure constitutes a remarkable breakthrough in the interpretation of the ultrasonic testing on this type of component.

  11. A mutation in the envelope protein fusion loop attenuates mouse neuroinvasiveness of the NY99 strain of West Nile virus

    International Nuclear Information System (INIS)

    Zhang Shuliu; Li Li; Woodson, Sara E.; Huang, Claire Y.-H.; Kinney, Richard M.; Barrett, Alan D.T.; Beasley, David W.C.

    2006-01-01

    Substitutions were engineered individually and in combinations at the fusion loop, receptor-binding domain and a stem-helix structure of the envelope protein of a West Nile virus strain, NY99, and their effects on mouse virulence and presentation of epitopes recognized by monoclonal antibodies (MAbs) were assessed. A single substitution within the fusion loop (L107F) attenuated mouse neuroinvasiveness of NY99. No substitutions attenuated NY99 neurovirulence. The L107F mutation also abolished binding of a non-neutralizing MAb, 3D9, whose epitope had not been previously identified. MAb 3D9 was subsequently shown to be broadly cross-reactive with other flaviviruses, consistent with binding near the highly conserved fusion loop

  12. Evaluation of MLACF based calculated attenuation brain PET imaging for FDG patient studies

    Science.gov (United States)

    Bal, Harshali; Panin, Vladimir Y.; Platsch, Guenther; Defrise, Michel; Hayden, Charles; Hutton, Chloe; Serrano, Benjamin; Paulmier, Benoit; Casey, Michael E.

    2017-04-01

    Calculating attenuation correction for brain PET imaging rather than using CT presents opportunities for low radiation dose applications such as pediatric imaging and serial scans to monitor disease progression. Our goal is to evaluate the iterative time-of-flight based maximum-likelihood activity and attenuation correction factors estimation (MLACF) method for clinical FDG brain PET imaging. FDG PET/CT brain studies were performed in 57 patients using the Biograph mCT (Siemens) four-ring scanner. The time-of-flight PET sinograms were acquired using the standard clinical protocol consisting of a CT scan followed by 10 min of single-bed PET acquisition. Images were reconstructed using CT-based attenuation correction (CTAC) and used as a gold standard for comparison. Two methods were compared with respect to CTAC: a calculated brain attenuation correction (CBAC) and MLACF based PET reconstruction. Plane-by-plane scaling was performed for MLACF images in order to fix the variable axial scaling observed. The noise structure of the MLACF images was different compared to those obtained using CTAC and the reconstruction required a higher number of iterations to obtain comparable image quality. To analyze the pooled data, each dataset was registered to a standard template and standard regions of interest were extracted. An SUVr analysis of the brain regions of interest showed that CBAC and MLACF were each well correlated with CTAC SUVrs. A plane-by-plane error analysis indicated that there were local differences for both CBAC and MLACF images with respect to CTAC. Mean relative error in the standard regions of interest was less than 5% for both methods and the mean absolute relative errors for both methods were similar (3.4%  ±  3.1% for CBAC and 3.5%  ±  3.1% for MLACF). However, the MLACF method recovered activity adjoining the frontal sinus regions more accurately than CBAC method. The use of plane-by-plane scaling of MLACF images was found to be a

  13. Chirped or time modulated excitation compared to short pulses for photoacoustic imaging in acoustic attenuating media

    Science.gov (United States)

    Burgholzer, P.; Motz, C.; Lang, O.; Berer, T.; Huemer, M.

    2018-02-01

    In photoacoustic imaging, optically generated acoustic waves transport the information about embedded structures to the sample surface. Usually, short laser pulses are used for the acoustic excitation. Acoustic attenuation increases for higher frequencies, which reduces the bandwidth and limits the spatial resolution. One could think of more efficient waveforms than single short pulses, such as pseudo noise codes, chirped, or harmonic excitation, which could enable a higher information-transfer from the samples interior to its surface by acoustic waves. We used a linear state space model to discretize the wave equation, such as the Stoke's equation, but this method could be used for any other linear wave equation. Linear estimators and a non-linear function inversion were applied to the measured surface data, for onedimensional image reconstruction. The proposed estimation method allows optimizing the temporal modulation of the excitation laser such that the accuracy and spatial resolution of the reconstructed image is maximized. We have restricted ourselves to one-dimensional models, as for higher dimensions the one-dimensional reconstruction, which corresponds to the acoustic wave without attenuation, can be used as input for any ultrasound imaging method, such as back-projection or time-reversal method.

  14. Feasibility Study of an Airbag-Based Crew Impact Attenuation System for the Orion MPCV

    Science.gov (United States)

    Do, Sydney; deWeck, Olivier

    2011-01-01

    Airbag-based methods for crew impact attenuation have been highlighted as a potential lightweight means of enabling safe land-landings for the Orion Multi-Purpose Crew Vehicle, and the next generation of ballistic shaped spacecraft. To investigate the performance feasibility of this concept during a nominal 7.62m/s Orion landing, a full-scale personal airbag system 24% lighter than the Orion baseline has been developed, and subjected to 38 drop tests on land. Through this effort, the system has demonstrated the ability to maintain the risk of injury to an occupant during a 7.85m/s, 0 deg. impact angle land-landing to within the NASA specified limit of 0.5%. In accomplishing this, the airbag-based crew impact attenuation concept has been proven to be feasible. Moreover, the obtained test results suggest that by implementing anti-bottoming airbags to prevent direct contact between the system and the landing surface, the system performance during landings with 0 deg impact angles can be further improved, by at least a factor of two. Additionally, a series of drop tests from the nominal Orion impact angle of 30 deg indicated that severe injury risk levels would be sustained beyond impact velocities of 5m/s. This is a result of the differential stroking of the airbags within the system causing a shearing effect between the occupant seat structure and the spacecraft floor, removing significant stroke from the airbags.

  15. Sulfated Hexasaccharides Attenuate Metastasis by Inhibition of P-selectin and Heparanase1

    Science.gov (United States)

    Borsig, Lubor; Vlodavsky, Israel; Ishai-Michaeli, Rivka; Torri, Giangiacomo; Vismara, Elena

    2011-01-01

    Development of compounds that target both heparanase and selectins is emerging as a promising approach for cancer therapy. Selectins are vascular cell adhesion molecules that mediate tumor cell interactions with platelets, leukocytes, and the vascular endothelium. Heparanase is an endoglycosidase that degrades heparan sulfate in the tumor microenvironment, cell surfaces, and vessel wall. Acting together, these molecules facilitate tumor cell arrest, extravasation, and metastasis. Here, we report the preparation of novel semisynthetic sulfated tri mannose C-C-linked dimers (STMCs) endowed with heparanase and selectin inhibitory activity. The P-selectin specificity of the STMC was defined by the anomeric linkage of the C-C bond. This STMC hexasaccharide is an effective inhibitor of P-selectin in vivo. We show that selective inhibition of heparanase attenuates metastasis in B16-BL6 melanoma cells, expressing high levels of this endoglycosidase, but has no effect on the metastasis of MC-38 carcinoma cells that express little or no heparanase activity. P-selectin-specific STMC attenuated metastasis in both animal models, indicating that inhibition of tumor cell interaction with the vascular endothelium is critical for cancer dissemination. Thus, the small size, the stability of the C-C bond, and the chemically defined structure of the newly generated STMCs make them superior to heparin derivatives and signify STMCs as valuable candidates for further evaluation. PMID:21532885

  16. Sulfated Hexasaccharides Attenuate Metastasis by Inhibition of P-selectin and Heparanase

    Directory of Open Access Journals (Sweden)

    Lubor Borsig

    2011-05-01

    Full Text Available Development of compounds that target both heparanase and selectins is emerging as a promising approach for cancer therapy. Selectins are vascular cell adhesion molecules that mediate tumor cell interactions with platelets, leukocytes, and the vascular endothelium. Heparanase is an endoglycosidase that degrades heparan sulfate in the tumor microenvironment, cell surfaces, and vessel wall. Acting together, these molecules facilitate tumor cell arrest, extravasation, and metastasis. Here, we report the preparation of novel semisynthetic sulfated tri mannose C-C-linked dimers (STMCs endowed with heparanase and selectin inhibitory activity. The P-selectin specificity of the STMC was defined by the anomeric linkage of the C-C bond. This STMC hexasaccharide is an effective inhibitor of P-selectin in vivo. We show that selective inhibition of heparanase attenuates metastasis in B16-BL6 melanoma cells, expressing high levels of this endoglycosidase, but has no effect on the metastasis of MC-38 carcinoma cells that express little or no heparanase activity. P-selectin-specific STMC attenuated metastasis in both animal models, indicating that inhibition of tumor cell interaction with the vascular endothelium is critical for cancer dissemination. Thus, the small size, the stability of the C-C bond, and the chemically defined structure of the newly generated STMCs make them superior to heparin derivatives and signify STMCs as valuable candidates for further evaluation.

  17. 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

  18. A self-adaptive metamaterial beam with digitally controlled resonators for subwavelength broadband flexural wave attenuation

    Science.gov (United States)

    Li, Xiaopeng; Chen, Yangyang; Hu, Gengkai; Huang, Guoliang

    2018-04-01

    Designing lightweight materials and/or structures for broadband low-frequency noise/vibration mitigation is an issue of fundamental importance both practically and theoretically. In this paper, by leveraging the concept of frequency-dependent effective stiffness control, we numerically and experimentally demonstrate, for the first time, a self-adaptive metamaterial beam with digital circuit controlled mechanical resonators for strong and broadband flexural wave attenuation at subwavelength scales. The digital controllers that are capable of feedback control of piezoelectric shunts are integrated into mechanical resonators in the metamaterial, and the transfer function is semi-analytically determined to realize an effective bending stiffness in a quadratic function of the wave frequency for adaptive band gaps. The digital as well as analog control circuits as the backbone of the system are experimentally realized with the guarantee stability of the whole electromechanical system in whole frequency regions, which is the most challenging problem so far. Our experimental results are in good agreement with numerical predictions and demonstrate the strong wave attenuation in almost a three times larger frequency region over the bandwidth of a passive metamaterial. The proposed metamaterial could be applied in a range of applications in the design of elastic wave control devices.

  19. Attenuation of monkeypox virus by deletion of genomic regions

    Science.gov (United States)

    Lopera, Juan G.; Falendysz, Elizabeth A.; Rocke, Tonie E.; Osorio, Jorge E.

    2015-01-01

    Monkeypox virus (MPXV) is an emerging pathogen from Africa that causes disease similar to smallpox. Two clades with different geographic distributions and virulence have been described. Here, we utilized bioinformatic tools to identify genomic regions in MPXV containing multiple virulence genes and explored their roles in pathogenicity; two selected regions were then deleted singularly or in combination. In vitro and in vivostudies indicated that these regions play a significant role in MPXV replication, tissue spread, and mortality in mice. Interestingly, while deletion of either region led to decreased virulence in mice, one region had no effect on in vitro replication. Deletion of both regions simultaneously also reduced cell culture replication and significantly increased the attenuation in vivo over either single deletion. Attenuated MPXV with genomic deletions present a safe and efficacious tool in the study of MPX pathogenesis and in the identification of genetic factors associated with virulence.

  20. Antioxidant treatment attenuates lactate production in diabetic nephropathy

    DEFF Research Database (Denmark)

    Laustsen, Christoffer; Nielsen, Per Mose; Stokholm Nørlinger, Thomas

    2017-01-01

    -IDEAL spiral sequence. Untreated diabetic rats showed increased renal lactate production compared with that shown by the controls. However, chronic TEMPOL treatment significantly attenuated diabetes-induced lactate production. No significant effects of diabetes or TEMPOL were observed on [13C]alanine levels......, indicating an intact glucose-alanine cycle, or [13C]bicarbonate, indicating normal flux through the Krebs cycle. In conclusion, this study demonstrates that diabetes-induced pseudohypoxia, as indicated by an increased lactate-to-pyruvate ratio, is significantly attenuated by antioxidant treatment......The early progression of diabetic nephropathy is notoriously difficult to detect and quantify before the occurrence of substantial histological damage. Recently, hyperpolarized [1-13C]pyruvate has demonstrated increased lactate production in the kidney early after the onset of diabetes, implying...

  1. ASSESSING AEROBIC NATURAL ATTENUATION OF TRICHLOROETHENE AT FOUR DOE SITES

    International Nuclear Information System (INIS)

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

    2005-01-01

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

  2. Plasma-parameter measurements using neutral-particle-beam attenuation

    International Nuclear Information System (INIS)

    Foote, J.H.; Molvik, A.W.; Turner, W.C.

    1982-01-01

    Intense and energetic neutral-particle-beam injection used for fueling or heating magnetically confined, controlled-fusion experimental plasmas can also provide diagnostic measurements of the plasmas. The attenuation of an atomic beam (mainly from charge-exchange and ionization interactions) when passing through a plasma gives the plasma line density. Orthogonal arrays of highly collimated detectors of the secondary-electron-emission type have been used in magnetic-mirror experiments to measure neutral-beam attenuation along chords through the plasma volume at different radial and axial positions. The radial array is used to infer the radial plasma-density profile; the axial array, to infer the axial plasma-density profile and the ion angular distribution at the plasma midplane

  3. A novel live-attenuated vaccine candidate for mayaro Fever.

    Directory of Open Access Journals (Sweden)

    William J Weise

    2014-08-01

    Full Text Available Mayaro virus (MAYV is an emerging, mosquito-borne alphavirus that causes a dengue-like illness in many regions of South America, and which has the potential to urbanize. Because no specific treatment or vaccine is available for MAYV infection, we capitalized on an IRES-based approach to develop a live-attenuated MAYV vaccine candidate. Testing in infant, immunocompetent as well as interferon receptor-deficient mice demonstrated a high degree of attenuation, strong induction of neutralizing antibodies, and efficacy against lethal challenge. This vaccine strain was also unable to infect mosquito cells, a major safety feature for a live vaccine derived from a mosquito-borne virus. Further preclinical development of this vaccine candidate is warranted to protect against this important emerging disease.

  4. Attenuation correction factors for cylindrical, disc and box geometry

    International Nuclear Information System (INIS)

    Agarwal, Chhavi; Poi, Sanhita; Mhatre, Amol; Goswami, A.; Gathibandhe, M.

    2009-01-01

    In the present study, attenuation correction factors have been experimentally determined for samples having cylindrical, disc and box geometry and compared with the attenuation correction factors calculated by Hybrid Monte Carlo (HMC) method [ C. Agarwal, S. Poi, A. Goswami, M. Gathibandhe, R.A. Agrawal, Nucl. Instr. and. Meth. A 597 (2008) 198] and with the near-field and far-field formulations available in literature. It has been observed that the near-field formulae, although said to be applicable at close sample-detector geometry, does not work at very close sample-detector configuration. The advantage of the HMC method is that it is found to be valid for all sample-detector geometries.

  5. Sustainability of natural attenuation of nitrate in agricultural aquifers

    Science.gov (United States)

    Green, Christopher T.; Bekins, Barbara A.

    2010-01-01

    Increased concentrations of nitrate in groundwater in agricultural areas, coinciding with increased use of chemical and organic fertilizers, have raised concern because of risks to environmental and human health. At some sites, these problems are mitigated by natural attenuation of nitrate as a result of microbially mediated reactions. Results from U.S. Geological Survey (USGS) research under the National Water-Quality Assessment (NAWQA) program show that reactions of dissolved nitrate with solid aquifer minerals and organic carbon help lower nitrate concentrations in groundwater beneath agricultural fields. However, increased fluxes of nitrate cause ongoing depletion of the finite pool of solid reactants. Consumption of the solid reactants diminishes the capacity of the aquifer to remove nitrate, calling into question the long-term sustainability of these natural attenuation processes.

  6. Attenuation of Vibrio fischeri quorum sensing using rationally designed polymers.

    Science.gov (United States)

    Piletska, Elena V; Stavroulakis, Georgios; Karim, Kal; Whitcombe, Michael J; Chianella, Iva; Sharma, Anant; Eboigbodin, Kevin E; Robinson, Gary K; Piletsky, Sergey A

    2010-04-12

    A first attempt to attenuate the quorum sensing (QS) of a marine heterotroph microorganism, Vibrio fischeri , using signal molecule-sequestering polymers (SSPs) is presented. A set of rationally designed polymers with affinity toward a signal molecule of V. fischeri , N-(beta-ketocaproyl)-l-homoserine lactone (3-oxo-C6-AHL) was produced. It is reported that computationally designed polymers could sequester a signal molecule of V. fischeri and prevent QS-controlled phenotypes (in this case, bioluminescence) from being up-regulated. It was proven that the attenuation of bioluminescence of V. fischeri was due to sequestration of the signal molecule by specific polymers and not due to the toxicity of polymer or nonspecific depletion of nutrients. The ability to disrupt the bacterial communication using easy to synthesize and chemically inert polymers could provide a new concept for the development of pharmaceuticals and susceptible device coatings such as catheters.

  7. Signal Attenuation Curve for Different Surface Detector Arrays

    Science.gov (United States)

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

    2014-06-01

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

  8. Anatomy of the TAMA SAS seismic attenuation system

    International Nuclear Information System (INIS)

    Marka, Szabolcs; Takamori, Akiteru; Ando, Masaki; Bertolini, Alessandro; Cella, Giancarlo; DeSalvo, Riccardo; Fukushima, Mitsuhiro; Iida, Yukiyoshi; Jacquier, Florian; Kawamura, Seiji; Nishi, Yuhiko; Numata, Kenji; Sannibale, Virginio; Somiya, Kentaro; Takahashi, Ryutaro; Tariq, Hareem; Tsubono, Kimio; Ugas, Jose; Viboud, Nicolas; Wang Chenyang; Yamamoto, Hiroaki; Yoda, Tatsuo

    2002-01-01

    The TAMA SAS seismic attenuation system was developed to provide the extremely high level of seismic isolation required by the next generation of interferometric gravitational wave detectors to achieve the desired sensitivity at low frequencies. Our aim was to provide good performance at frequencies above ∼10 Hz, while utilizing only passive subsystems in the sensitive frequency band of the TAMA interferometric gravitational wave detectors. The only active feedback is relegated below 6 Hz and it is used to damp the rigid body resonances of the attenuation chain. Simulations, based on subsystem performance characterizations, indicate that the system can achieve rms mirror residual motion measured in a few tens of nanometres. We will give a brief overview of the subsystems and point out some of the characterization results, supporting our claims of achieved performance. SAS is a passive, UHV compatible and low cost system. It is likely that extremely sensitive experiments in other fields will also profit from our study

  9. 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

  10. The UV attenuation in JWST target VV 191

    Science.gov (United States)

    Holwerda, Benne

    2017-08-01

    We aim to map the UV-near-IR attenuation curve along many sightlines within nearby disk galaxies to resolve a large fundamental uncertainty in galaxy evolution studies: the variance in the attenuation curve within an indivual galaxy disk on linear scales relatively blue elliptical beautifully backlights the outer disk of a foreground face-on spiral galaxy.Dither strategy:We opt for a 2-point dither in the case of the F336W observations (1 orbit) and a 3pt dither strategy for the F225W observations. The 9 orbits for the F225W observations are broken into three groupings of 3 orbits in the 3 dither pattern. This is to ensure correction of cosmics and detector artifacts. Our secondary aim is an HST/JWST image with good public outreach potential and our aim is to maximize image quality for this reason as well.

  11. Is Necessary Attenuation Correction for Cat Brain PET?

    International Nuclear Information System (INIS)

    Kim, Jin Su; Lee, Jae Sung; Park, Min Hyun; Im, Ki Chun; Oh, Seung Ha; Lee, Dong Soo; Moon, Dae Hyuk

    2007-01-01

    Photon attenuation and scatter corrections (AC and SC) were necessary for quantification of human PET. However, there is no consensus on whether AC and SC are necessary for the cat brain PET imaging. Since post-injection transmission (TX) PET scans are not permitted or provided to microPET scanner users at present, additional time for performing TX scan and awaiting FDG uptake is required for attenuation and scatter corrections. Increasing probability of subject movement and possible biological effect of long term anesthesia would be the problem in additional TX scan. The aim of this study was to examine the effect of AC and SC for the quantification of cat brain PET data

  12. Utilization of barite/cement composites for gamma rays attenuation

    Science.gov (United States)

    Sakr, Khaled; Ramadan, Wageeh; Sayed, Magda; El-Zakla, Tarek; El-Desouqy, Mohamed; El-Faramawy, Nabil

    2018-04-01

    The present work is directed to investigate the contribution of adding barite aggregates to cement as a shielding material for radioactive wastes disposal facilities. The percentages of barite from 5% up to 20% mixed with cement with different grain sizes were examined. Mechanical and physical properties such as compressive strength, wet and dry densities, water absorption, and porosity have been investigated. The thermogravimetric analysis and X-ray diffraction were used to examine the thermal stability and the characterizations of studied samples, respectively. The linear attenuation coefficient, mean free path, half value layer, and transmission fraction were evaluated. All the nuclear shielding parameters revealed the uppermost values for cement mixed with 5% barite of size range 250-600 µm. The attenuation coefficient of the investigated samples displayed an increase by more than 125% than that of neat cement.

  13. Effects of methods of attenuation correction on source parameter determination

    Science.gov (United States)

    Sonley, Eleanor; Abercrombie, Rachel E.

    We quantify the effects of using different approaches to model individual earthquake spectra. Applying different approaches can introduce significant variability in the calculated source parameters, even when applied to the same data. To compare large and small earthquake source parameters, the results of multiple studies need to be combined to extend the magnitude range, but the variability introduced by the different approaches hampers the outcome. When studies are combined, there is large uncertainty and large scatter and some systematic differences have been neglected. We model individual earthquake spectra from repeating earthquakes (M˜2) at Parkfield, CA, recorded by a borehole network. We focus on the effects of trade-offs between attenuation (Q) and corner frequency in spectral fitting and the effect of the model shape at the corner frequency on radiated energy. The trade-off between attenuation and corner frequency can increase radiated energy by up to 400% and seismic moment by up to 100%.

  14. A Yersinia pestis tat mutant is attenuated in bubonic and small-aerosol pneumonic challenge models of infection but not as attenuated by intranasal challenge.

    Directory of Open Access Journals (Sweden)

    Joel Bozue

    Full Text Available Bacterial proteins destined for the Tat pathway are folded before crossing the inner membrane and are typically identified by an N-terminal signal peptide containing a twin arginine motif. Translocation by the Tat pathway is dependent on the products of genes which encode proteins possessing the binding site of the signal peptide and mediating the actual translocation event. In the fully virulent CO92 strain of Yersinia pestis, the tatA gene was deleted. The mutant was assayed for loss of virulence through various in vitro and in vivo assays. Deletion of the tatA gene resulted in several consequences for the mutant as compared to wild-type. Cell morphology of the mutant bacteria was altered and demonstrated a more elongated form. In addition, while cultures of the mutant strain were able to produce a biofilm, we observed a loss of adhesion of the mutant biofilm structure compared to the biofilm produced by the wild-type strain. Immuno-electron microscopy revealed a partial disruption of the F1 antigen on the surface of the mutant. The virulence of the ΔtatA mutant was assessed in various murine models of plague. The mutant was severely attenuated in the bubonic model with full virulence restored by complementation with the native gene. After small-particle aerosol challenge in a pneumonic model of infection, the mutant was also shown to be attenuated. In contrast, when mice were challenged intranasally with the mutant, very little difference in the LD50 was observed between wild-type and mutant strains. However, an increased time-to-death and delay in bacterial dissemination was observed in mice infected with the ΔtatA mutant as compared to the parent strain. Collectively, these findings demonstrate an essential role for the Tat pathway in the virulence of Y. pestis in bubonic and small-aerosol pneumonic infection but less important role for intranasal challenge.

  15. Sound Attenuation in Elliptic Mufflers Using a Regular Perturbation Method

    OpenAIRE

    Banerjee, Subhabrata; Jacobi, Anthony M.

    2012-01-01

    The study of sound attenuation in an elliptical chamber involves the solution of the Helmholtz equation in elliptic coordinate systems. The Eigen solutions for such problems involve the Mathieu and the modified Mathieu functions. The computation of such functions poses considerable challenge. An alternative method to solve such problems had been proposed in this paper. The elliptical cross-section of the muffler has been treated as a perturbed circle, enabling the use of a regular perturbatio...

  16. Dissipative Control Systems and Disturbance Attenuation for Nonlinear H∞ Problems

    International Nuclear Information System (INIS)

    Frankowska, H.; Quincampoix, M.

    1999-01-01

    We characterize functions satisfying a dissipative inequality associated with a control problem. Such a characterization is provided in terms of an epicontingent solution, or a viscosity supersolution to a partial differential equation called Isaacs' equation. Links between supersolutions and epicontingent solutions to Isaacs' equation are studied. Finally, we derive (possibly discontinuous) disturbance attenuation feedback of the H ∞ problem from contingent formulation of Isaacs' equation

  17. DEVELOPEMENT OF A LIGHT ATTENUATOR BASED ON GLASSY ...

    African Journals Online (AJOL)

    30 juin 2012 ... d'atténuation réel variant de 63% à l'extinction dans une plage angulaire de 0 à 70°. 5. RÉFÉRENCES. [1] Jeong Y. S., Bae S. C., Jung Y., Oh K. Micro-optical waveguide on micro-actuating platform and its application in variable optical attenuator. Optical Fiber Technology. 2006, 12, 38– 47. Laser.

  18. Gamma-ray self-attenuation corrections in environmental samples

    International Nuclear Information System (INIS)

    Robu, E.; Giovani, C.

    2009-01-01

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

  19. Cavity Attenuated Phase Shift (CAPS) Monitor Instrument Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Sedlacek, Arthur J. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2016-04-01

    The CAPS PMex monitor is a cavity attenuated phase shift extinction instrument. It operates as an optical extinction spectrometer, using a visible-light-emitting diode (LED) as the light source, a sample cell incorporating two high-reflectivity mirrors centered at the wavelength of the LED, and a vacuum photodiode detector. Its efficacy is based on the fact that aerosols are broadband scatterers and absorbers of light.

  20. PO2 Cycling Reduces Diaphragm Fatigue by Attenuating ROS Formation

    OpenAIRE

    Zuo, Li; Diaz, Philip T.; Chien, Michael T.; Roberts, William J.; Kishek, Juliana; Best, Thomas M.; Wagner, Peter D.

    2014-01-01

    Prolonged muscle exposure to low PO2 conditions may cause oxidative stress resulting in severe muscular injuries. We hypothesize that PO2 cycling preconditioning, which involves brief cycles of diaphragmatic muscle exposure to a low oxygen level (40 Torr) followed by a high oxygen level (550 Torr), can reduce intracellular reactive oxygen species (ROS) as well as attenuate muscle fatigue in mouse diaphragm under low PO2. Accordingly, dihydrofluorescein (a fluorescent probe) was used to monito...

  1. Attenuation of fast neutron in concretes for biological shielding

    International Nuclear Information System (INIS)

    Labrada, A.; Chavez, A.; Gonzalez Mateu, D.; Desdin, F.; Tenjeiro, J.I.; Tellez, E.

    1993-01-01

    The attenuation of neutrons emitted by an 10 6 n/s. Am-Be source, in concretes elaborated with different aggregates is discussed in this paper. Two measurement methods were used an dosimetric system with Bonner spheres and 6 LiI(Eu) detector, and LAVSAN dielectric nuclear track detectors - with 238 U converts. The concretes elaborated with magnetite is reported as the best for neutron shielding while the Bauxite is not advisable for this purpose

  2. Interlaboratory comparison of radiation-induced attenuation in optical fibers

    International Nuclear Information System (INIS)

    Friebele, E.J.; Lyons, P.B.; Blackburn, J.C.

    1989-08-01

    A comparison of the losses induced in step index multimode, graded index multimode and single mode fibers by pulsed radiation exposure has been made among 12 laboratories over a period of 5 years. The recoveries of the incremental attenuations from 10 -9 to 10 1 s are reported. Although a standard set of measurement parameters was attempted, differences between the laboratories are evident; possible origins for these are discussed. 18 refs., 18 figs., 7 tabs

  3. Peripheral δ-opioid receptors attenuate the exercise pressor reflex.

    Science.gov (United States)

    Leal, Anna K; Yamauchi, Katsuya; Kim, Joyce; Ruiz-Velasco, Victor; Kaufman, Marc P

    2013-10-15

    In rats with ligated femoral arteries, the exercise pressor reflex is exaggerated, an effect that is attenuated by stimulation of peripheral μ-opioid receptors on group IV metabosensitive afferents. In contrast, δ-opioid receptors are expressed mostly on group III mechanosensitive afferents, a finding that prompted us to determine whether stimulation of these opioid receptors could also attenuate the exaggerated exercise pressor reflex in "ligated" rats. We found femoral arterial injection of [D-Pen2,D-Pen5]enkephalin (DPDPE; 1.0 μg), a δ-opioid agonist, significantly attenuated the pressor and cardioaccelerator components of the exercise pressor reflex evoked by hindlimb muscle contraction in both rats with ligated and patent femoral arteries. DPDPE significantly decreased the pressor responses to muscle mechanoreflex activation, evoked by tendon stretch, in ligated rats only. DPDPE (1.0 μg) had no effect in either group on the pressor and cardioaccelerator responses to capsaicin (0.2 μg), which primarily stimulates group IV afferents. DPDPE (1.0 μg) had no effect on the pressor and cardioaccelerator responses to lactic acid (24 mM), which stimulates group III and IV afferents, in rats with patent femoral arteries but significantly decreased the pressor response in ligated rats. Western blots revealed the amount of protein comprising the δ-opioid receptor was greater in dorsal root ganglia innervating hindlimbs with ligated femoral arteries than in dorsal root ganglia innervating hindlimbs with patent femoral arteries. Our findings support the hypothesis that stimulation of δ-opioid receptors on group III afferents attenuated the exercise pressor reflex.

  4. Relationship between attenuation coefficients and dose-spread kernels

    International Nuclear Information System (INIS)

    Boyer, A.L.

    1988-01-01

    Dose-spread kernels can be used to calculate the dose distribution in a photon beam by convolving the kernel with the primary fluence distribution. The theoretical relationships between various types and components of dose-spread kernels relative to photon attenuation coefficients are explored. These relations can be valuable as checks on the conservation of energy by dose-spread kernels calculated by analytic or Monte Carlo methods

  5. 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.

  6. Comparative genomic analysis of Brucella abortus vaccine strain 104M reveals a set of candidate genes associated with its virulence attenuation.

    Science.gov (United States)

    Yu, Dong; Hui, Yiming; Zai, Xiaodong; Xu, Junjie; Liang, Long; Wang, Bingxiang; Yue, Junjie; Li, Shanhu

    2015-01-01

    The Brucella abortus strain 104M, a spontaneously attenuated strain, has been used as a vaccine strain in humans against brucellosis for 6 decades in China. Despite many studies, the molecular mechanisms that cause the attenuation are still unclear. Here, we determined the whole-genome sequence of 104M and conducted a comprehensive comparative analysis against the whole genome sequences of the virulent strain, A13334, and other reference strains. This analysis revealed a highly similar genome structure between 104M and A13334. The further comparative genomic analysis between 104M and A13334 revealed a set of genes missing in 104M. Some of these genes were identified to be directly or indirectly associated with virulence. Similarly, a set of mutations in the virulence-related genes was also identified, which may be related to virulence alteration. This study provides a set of candidate genes associated with virulence attenuation in B.abortus vaccine strain 104M.

  7. 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.

  8. 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)

  9. Seismic Linear Noise Attenuation with Use of Radial Transform

    Science.gov (United States)

    Szymańska-Małysa, Żaneta

    2018-03-01

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

  10. Regionalization of ground motion attenuation in the conterminous United States

    International Nuclear Information System (INIS)

    Chung, D.H.; Bernreuter, D.L.

    1979-01-01

    Attenuation results from geometric spreading and from absorption. The former is almost independent of crustal geology or physiographic region. The latter depends strongly on crustal geology and the state of the earth's upper mantle. Except for very high-frequency waves, absorption does not affect ground motion at distances less than 25 to 50 km. Thus, in the near-field zone, the attenuation in the eastern United States will be similar to that in the western United States. Most of the differences in ground motion can be accounted for by differences in attenuation caused by differences in absorption. The other important factor is that for some Western earthquakes the fault breaks the earth's surface, resulting in larger ground motion. No Eastern earthquakes are known to have broken the earth's surface by faulting. The stress drop of Eastern earthquakes may be higher than for Western earthquakes of the same seismic moment, which would affect the high-frequency spectral content. This factor is believed to be of much less significance than differences in absorption in explaining the differences in ground motion between the East and the West. 6 figures

  11. Natural attenuation, biostimulation and bioaugmentation of landfill leachate management

    Science.gov (United States)

    Er, X. Y.; Seow, T. W.; Lim, C. K.; Ibrahim, Z.

    2018-04-01

    Landfills used for solid waste management will lead to leachate production. Proper leachate management is highly essential to be paid attention to protect the environment and living organisms’ health and safety. In this study, the remedial strategies used for leachate management were natural attenuation, biostimulation and bioaugmentation. All treatment samples were treated via 42-days combined anaerobic-aerobic treatment and the treatment efficiency was studied by measuring the removal rate of COD and ammonia nitrogen. In this study, all remedial strategies showed different degrees of contaminants removal. Lowest contaminants removal rate was achieved via bioaugmentation of B. panacihumi strain ZB1, which were 39.4% of COD and 37.6% of ammonia nitrogen removed from the leachate sample. Higher contaminants removal rate was achieved via natural attenuation and biostimulation. Native microbial population was able to remove 41% of COD and 59% of ammonia nitrogen from the leachate sample. The removal efficiency could be further improved via biostimulation to trigger microbial growth and decontamination rate. Through biostimulation, 58% of COD and 51.8% of ammonia nitrogen were removed from the leachate sample. In conclusion, natural attenuation and biostimulation should be the main choice for leachate management to avoid any unexpected impacts due to introduction of exogenous species.

  12. 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

  13. 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.

  14. MR constrained simultaneous reconstruction of activity and attenuation maps in brain TOF-PET/MR imaging

    Energy Technology Data Exchange (ETDEWEB)

    Mehranian, Abolfazl; Zaidi, Habib [Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, CH-1211 Geneva (Switzerland)

    2014-07-29

    The maximum likelihood estimation of attenuation and activity (MLAA) algorithm has been proposed to jointly estimate activity and attenuation from emission data only. Salomon et al employed the MLAA to estimate activity and attenuation from time-of-flight PET data with spatial MR prior information on attenuation. Recently, we proposed a novel algorithm to impose both spatial and statistical constraints on attenuation estimation within the MLAA algorithm using Dixon MR images and a constrained Gaussian mixture model (GMM). In this study, we compare the proposed algorithm with MLAA and MLAA-Salomon in brain TOF-PET/MR imaging.

  15. 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.

  16. MR constrained simultaneous reconstruction of activity and attenuation maps in brain TOF-PET/MR imaging

    International Nuclear Information System (INIS)

    Mehranian, Abolfazl; Zaidi, Habib

    2014-01-01

    The maximum likelihood estimation of attenuation and activity (MLAA) algorithm has been proposed to jointly estimate activity and attenuation from emission data only. Salomon et al employed the MLAA to estimate activity and attenuation from time-of-flight PET data with spatial MR prior information on attenuation. Recently, we proposed a novel algorithm to impose both spatial and statistical constraints on attenuation estimation within the MLAA algorithm using Dixon MR images and a constrained Gaussian mixture model (GMM). In this study, we compare the proposed algorithm with MLAA and MLAA_Salomon in brain TOF-PET/MR imaging.

  17. Variability in dynamic properties of tantalum : spall, attenuation and load/unload.

    Energy Technology Data Exchange (ETDEWEB)

    Furnish, Michael David; Reinhart, William Dodd; Trott, Wayne Merle; Vogler, Tracy John; Chhabildas, Lalit Chandra

    2005-07-01

    A suite of impact experiments was conducted to assess spatial and shot-to-shot variability in dynamic properties of tantalum. Samples had a uniform refined {approx}20 micron grain structure with a strong axisymmetric [111] crystallographic texture. Two experiments performed with sapphire windows (stresses of approximately 7 and 12 GPa) clearly showed elastic-plastic loading and slightly hysteretic unloading behavior. An HEL amplitude of 2.8 GPa (corresponding to Y 1.5 GPa) was observed. Free-surface spall experiments showed clear wave attenuation and spallation phenomena. Here, loading stresses were {approx} 12.5 GPa and various ratios of impactor to target thicknesses were used. Spatial and shot-to-shot variability of the spall strength was {+-} 20%, and of the HEL, {+-} 10%. Experiments conducted with smaller diameter flyer plates clearly showed edge effects in the line and point VISAR records, indicating lateral release speeds of roughly 5 km/s.

  18. Investigation of attenuation coefficients of some stainless steel and aluminum alloys

    Science.gov (United States)

    Caner, Zafer; Tufan, Mustafa ćaǧatay

    2018-02-01

    In this study, attenuation coefficients of two different stainless steel alloys (AISI 304 and AISI 310), which have a wide range of applications from home appliances to the automotive sector, and two different aluminum alloys (6013 and 5083), which have a high mechanical strength and a light weight structure and are used in many fields from aviation to military vehicles, has been determined. For this purpose, we used gamma spectrometer system with NaI(Tl) detector. In our measurements, we used Eu-152, Ra-226 and Co-60 as gamma ray sources. To narrow the beam of gamma rays, we designed the new steel based collimator. We also investigated the effect of using collimator. Obtained results were compared with the NIST XCOM values.

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

    DEFF Research Database (Denmark)

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

    2011-01-01

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

  20. MR-guided joint reconstruction of activity and attenuation in brain PET-MR

    DEFF Research Database (Denmark)

    Mehranian, Abolfazl; Zaidi, Habib; Reader, Andrew J

    2017-01-01

    by unknown scaling factors. We recently demonstrated that in hybrid PET-MR, the scaling issue of this algorithm can be effectively addressed by imposing MR spatial constraints on the estimation of attenuation maps using a penalized MLAA (P-MLAA(+)) algorithm. With the advent of simultaneous PET-MR systems......, MRI-guided PET image reconstruction has also gained attention for improving the quantitative accuracy of PET images, usually degraded by noise and partial volume effects. The aim of this study is therefore to increase the benefits of MRI information for improving the quantitative accuracy of PET...... as a reference. The simulation results showed that the proposed method can notably improve the visual quality of the PET images by reducing noise while preserving structural boundaries and at the same time improving the quantitative accuracy of the PET images. Our clinical reconstruction results showed...

  1. An avian cell line designed for production of highly attenuated viruses.

    Science.gov (United States)

    Jordan, Ingo; Vos, Ad; Beilfuss, Stefanie; Neubert, Andreas; Breul, Sabine; Sandig, Volker

    2009-01-29

    Several viral vaccines, including highly promising vectors such as modified vaccinia Ankara (MVA), are produced on chicken embryo fibroblasts. Dependence on primary cells complicates production especially in large vaccination programs. With primary cells it is also not possible to create packaging lines for replication-deficient vectors that are adapted to proliferation in an avian host. To obviate requirement for primary cells permanent lines from specific tissues of muscovy duck were derived (AGE1.CR, CS, and CA) and further modified: we demonstrate that stable expression of the structural gene pIX from human adenovirus increases titers for unrelated poxvirus in the avian cells. This augmentation appears to be mediated via induction of heat shock and thus provides a novel cellular substrate that may allow further attenuation of vaccine strains.

  2. Evaluating Attenuation of Vibration Response using Particle Impact Damping for a Range of Equipment Assemblies

    Science.gov (United States)

    Knight, Brent; Parsons, David; Smith, Andrew; Hunt, Ron; LaVerde, Bruce; Towner, Robert; Craigmyle, Ben

    2013-01-01

    Particle dampers provide a mechanism for diverting energy away from resonant structural vibrations. This experimental study provides data from a series of acoustically excited tests to determine the effectiveness of these dampers for equipment mounted to a curved orthogrid panel for a launch vehicle application. Vibration attenuation trends are examined for variations in particle damper fill level, component mass, and excitation energy. A significant response reduction at the component level was achieved, suggesting that comparatively small, strategically placed, particle damper devices might be advantageously used in launch vehicle design. These test results were compared to baseline acoustic response tests without particle damping devices, over a range of isolation and damping parameters. Instrumentation consisting of accelerometers, microphones, and still photography data will be collected to correlate with the analytical results.

  3. Safety and immunogenicity of a live attenuated Japanese encephalitis chimeric virus vaccine (IMOJEV®) in children.

    Science.gov (United States)

    Chokephaibulkit, K; Houillon, G; Feroldi, E; Bouckenooghe, A

    2016-01-01

    JE-CV (IMOJEV®, Sanofi Pasteur, France) is a live attenuated virus vaccine constructed by inserting coding sequences of the prM and E structural proteins of the Japanese encephalitis SA14-14-2 virus into the genome of yellow fever 17D virus. Primary immunization with JE-CV requires a single dose of the vaccine. This article reviews clinical trials of JE-CV in children aged up to 6 years conducted in countries across South-East Asia. Strong and persistent antibody responses were observed after single primary and booster doses, with 97% of children seroprotected up to five years after booster vaccination. Models of long-term antibody persistence predict a median duration of protection of approximately 30 years after a booster dose. The safety and reactogenicity profiles of JE-CV primary and booster doses are comparable to other widely used childhood vaccines.

  4. Model testing of a 10-kg high explosive blast attenuation maze

    International Nuclear Information System (INIS)

    Bacigalupi, C.M.; Burton, W.A.

    1981-01-01

    The basement area of the proposed High Explosive Applications Facility (HEAF) at the Lawrence Livermore National Laboratory includes 10-kg HE assembly and process cells, and a 10-kg corridor for the transport of up to 10 kg of HE from the receiving dock to the cells and to the experimental firing tanks. Previous model experiments developed a process cell-maze configuration that attenuated the effects of an accidental 10-kg detonation to acceptable levels (maximum of 10 to 11 psi reflected). This document reports 1/8-scale model tests conducted to confirm the maze design and to determine the blast pressures in adjacent areas in the final HEAF building configuration. In addition, pressure/time information was obtained at selected points in the model expansion chamber to provide the architect-engineer with information for structural design

  5. Housefly Larva Vermicomposting Efficiently Attenuates Antibiotic Resistance Genes in Swine Manure, with Concomitant Bacterial Population Changes.

    Science.gov (United States)

    Wang, Hang; Li, Hongyi; Gilbert, Jack A; Li, Haibo; Wu, Longhua; Liu, Meng; Wang, Liling; Zhou, Qiansheng; Yuan, Junxiang; Zhang, Zhijian

    2015-11-01

    Manure from swine treated with antimicrobials as feed additives is a major source for the expansion of the antibiotic resistance gene (ARG) reservoir in the environment. Vermicomposting via housefly larvae (Musca domestica) can be efficiently used to treat manure and regenerate biofertilizer, but few studies have investigated its effect on ARG attenuation. Here, we tracked the abundances of 9 ARGs and the composition and structure of the bacterial communities in manure samples across 6 days of full-scale manure vermicomposting. On day 6, the abundances of genes encoding tetracycline resistance [tet(M), tet(O), tet(Q), and tet(W)] were reduced (P biofertilizer in agroecosystems. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  6. Research on strength attenuation law of concrete in freezing - thawing environment

    Science.gov (United States)

    Xiao, qianhui; Cao, zhiyuan; Li, qiang

    2018-03-01

    By rapid freezing and thawing method, the experiments of concrete have been 300 freeze-thaw cycles specimens in the water. The cubic compression strength value under different freeze-thaw cycles was measured. By analyzing the test results, the water-binder ratio of the concrete under freeze-thaw environments, fly ash and air entraining agent is selected dosage recommendations. The exponential attenuation prediction model and life prediction model of compression strength of concrete under freezing-thawing cycles considering the factors of water-binder ratio, fly ash content and air-entraining agent dosage were established. The model provides the basis for predicting the durability life of concrete under freezing-thawing environment. It also provides experimental basis and references for further research on concrete structures with antifreeze requirements.

  7. Raman scattering and attenuated-total-reflection studies of surface-plasmon polaritons

    International Nuclear Information System (INIS)

    Kurosawa, K.; Pierce, R.M.; Ushioda, S.; Hemminger, J.C.

    1986-01-01

    We have made in situ measurements of attenuated total reflection (ATR) and Raman scattering from a layered structure consisting of a glass prism, a thin silver film, an MgF 2 spacer, and a liquid mixture whose refractive index is matched to that of MgF 2 . When the incident angle of the laser beam coincides with the ATR angle, the surface-plasmon polariton (SPP) of the silver film is excited resonantly and the Raman scattering intensity of the liquid shows a maximum. The same effect is observed at the frequency of the Stokes scattered light. By measuring the decrease of the Raman scattering intensity of the liquid with increase of the thickness of the MgF 2 spacer layer, we have determined the decay length (l/sub d/) of the SPP field into the liquid. The measured value of l/sub d/ = 1539 A agrees with the calculated value, 1534 A

  8. The infrared emission of carbonaceous particles around C-rich IRAS sources

    International Nuclear Information System (INIS)

    Blanco, A.; Borghesi, A.; Fonti, S.; Orofino, V.; Strafella, F.

    1997-01-01

    The IRAS spectra of 23 carbon-rich sources have been fitted by means of an improved theoretical model based on the Leung-Spagna radiative transfer code and using extinction data obtained in their laboratory for different types of amorphous carbon and silicon carbide submicron particles. The agreement between observations and theoretical spectra is rather good. A comparison between the IRAS spectrum of the object 12447 + 0425 (RU Vir) and that recently obtained at UKIRT, for the same object but with higher resolution, seems to open new problems

  9. Bipyrimidine Signatures as a Photoprotective Genome Strategy in G + C-rich Halophilic Archaea.

    Science.gov (United States)

    Jones, Daniel L; Baxter, Bonnie K

    2016-09-02

    Halophilic archaea experience high levels of ultraviolet (UV) light in their environments and demonstrate resistance to UV irradiation. DNA repair systems and carotenoids provide UV protection but do not account for the high resistance observed. Herein, we consider genomic signatures as an additional photoprotective strategy. The predominant forms of UV-induced DNA damage are cyclobutane pyrimidine dimers, most notoriously thymine dimers (T^Ts), which form at adjacent Ts. We tested whether the high G + C content seen in halophilic archaea serves a photoprotective function through limiting T nucleotides, and thus T^T lesions. However, this speculation overlooks the other bipyrimidine sequences, all of which capable of forming photolesions to varying degrees. Therefore, we designed a program to determine the frequencies of the four bipyrimidine pairs (5' to 3': TT, TC, CT, and CC) within genomes of halophilic archaea and four other randomized sample groups for comparison. The outputs for each sampled genome were weighted by the intrinsic photoreactivities of each dinucleotide pair. Statistical methods were employed to investigate intergroup differences. Our findings indicate that the UV-resistance seen in halophilic archaea can be attributed in part to a genomic strategy: high G + C content and the resulting bipyrimidine signature reduces the genomic photoreactivity.

  10. De toename van Anacamptis pyramidalis (L.) L.C. Rich. en Ophrys apifera Hudson in Nederland

    NARCIS (Netherlands)

    Kreutz, C.A.J.

    1994-01-01

    Until some ten years ago Anacamptis pyramidalis and Ophrys apifera were very rare in the Netherlands. In the last decade, however, both species have been found at many new localities. In this paper these are discussed and new distribution maps are presented.

  11. Enhancement of thermal neutron attenuation of nano-B4C, -BN dispersed neutron shielding polymer nanocomposites

    International Nuclear Information System (INIS)

    Kim, Jaewoo; Lee, Byung-Chul; Uhm, Young Rang; Miller, William H.

    2014-01-01

    Highlights: • Preparation of B 4 C and BN nanopowders using a simple ball milling process. • Homogeneous dispersion and strong adhesion of nano-B 4 C and -BN with polymer matrix. • Enhancement of mechanical properties of the nanocomposites compared to their micro counterparts. • Enhancement of thermal neutron attenuation of the nanocomposites. - Abstract: Nano-sized boron carbide (B 4 C) and boron nitride (BN) powder were prepared using ball milling. Micro- and milled nano-powders were melt blended with high density polyethylene (HDPE) using a polymer mixer followed by hot pressing to fabricate sheet composites. The tensile and flexural strengths of HDPE nanocomposites were ∼20% higher than their micro counterparts, while those for latter decreased compared to neat HDPE. Thermal neutrons attenuation of the prepared HDPE nanocomposites was evaluated using a monochromatic ∼0.025 eV neutron beam. Thermal neutron attenuation of the HDPE nanocomposites was greatly enhanced compared to their micro counterparts at the same B-10 areal densities. Monte Carlo n-Particles (MCNP) simulations based on the lattice structure modeling also shows the similar filler size dependent thermal neutron absorption

  12. Heterogeneities of the shear wave attenuation field in the lithosphere of East Tien Shan and their relationship with seismicity

    Science.gov (United States)

    Kopnichev, Yu. F.; Sokolova, I. N.

    2012-02-01

    The shear wave attenuation field in the lithosphere of Eastern Tien Shan has been mapped. The method based on analysis of the ratio between amplitudes of Sn and Pn waves was used. On aggregate, about 120 seismograms made at the Makanchi station (MKAR), mainly in the period of 2003-2009, at epicentral distances of about 350-1200 km were analyzed. It was found that shear wave attenuation in the lithosphere of Eastern Tien Shan is weaker than that in the region of Central Tien Shan. This agrees with the fact that the rate of deformation of the Earth's crust in Eastern Tien Shan is lower (based on GPS data), as is the seismicity level, in comparison to Central Tien Shan. The zones of high attenuation, where strong earthquakes with M > 7.0 have not occurred for the last 200 years, have been identified: first of all, these are the area west of Urumqi and that of the Lop Nur test site. It is suggested that in the first zone, where an annular seismicity structure has formed over the last 30 years, a strong earthquake may be being prepared. The second zone is most probably related to the uplift of mantle fluids resulting from a long-term intensive technogenic effect, analogous to what has occurred in areas of other nuclear test sites (Nevada and Semipalatinsk).

  13. Fast neutron (14 MeV) attenuation analysis in saturated core samples and its application in well logging

    International Nuclear Information System (INIS)

    Amin Attarzadeh; Mohammad Kamal Ghassem Al Askari; Tagy Bayat

    2009-01-01

    To introduce the application of nuclear logging, it is appropriate to provide a motivation for the use of nuclear measurement techniques in well logging. Importance aspects of the geological sciences are for instance grain and porosity structure and porosity volume of the rocks, as well as the transport properties of a fluid in the porous media. Nuclear measurements are, as a rule non-intrusive. Namely, a measurement does not destroy the sample, and it does not interfere with the process to be measured. Also, non- intrusive measurements are often much faster than the radiation methods, and can also be applied in field measurements. A common type of nuclear measurement employs neutron irradiation. It is powerful technique for geophysical analysis. In this research we illustrate the detail of this technique and it's applications to well logging and oil industry. Experiments have been performed to investigate the possibilities of using neutron attenuation measurements to determine water and oil content of rock sample. A beam of 14 MeV neutrons produced by a 150 KV neutron generator was attenuated by different samples and subsequently detected with plastic scintillators NE102 (Fast counter). Each sample was saturated with water and oil. The difference in neutron attenuation between dry and wet samples was compared with the fluid content determined by mass balance of the sample. In this experiment we were able to determine 3% of humidity in standard sample model (SiO 2 ) and estimate porosity in geological samples when saturated with different fluids. (Author)

  14. Enhancement of thermal neutron attenuation of nano-B{sub 4}C, -BN dispersed neutron shielding polymer nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jaewoo, E-mail: kimj@kaeri.re.kr [Nuclear Materials Research Division, Korea Atomic Energy Research Institute, 111-989 Daeduck-daero, Yuseong-gu, Daejeon-si 305-353 (Korea, Republic of); WCI Quantum Beam based Radiation Research Center, Korea Atomic Energy Research Institute, 111-989 Daeduck-daero, Yuseong-gu, Daejeon-si 305-353 (Korea, Republic of); Missouri University Research Reactor, University of Missouri-Columbia, Columbia, MO 65211 (United States); Lee, Byung-Chul [Nuclear Reactor Core Design Division, Korea Atomic Energy Research Institute, 111-989 Daeduck-daero, Yuseong-gu, Daejeon-si 305-353 (Korea, Republic of); Uhm, Young Rang [Radioisotopes Research Division, Korea Atomic Energy Research Institute, 111-989 Daeduck-daero, Yuseong-gu, Daejeon-si 305-353 (Korea, Republic of); Miller, William H. [Missouri University Research Reactor, University of Missouri-Columbia, Columbia, MO 65211 (United States)

    2014-10-15

    Highlights: • Preparation of B{sub 4}C and BN nanopowders using a simple ball milling process. • Homogeneous dispersion and strong adhesion of nano-B{sub 4}C and -BN with polymer matrix. • Enhancement of mechanical properties of the nanocomposites compared to their micro counterparts. • Enhancement of thermal neutron attenuation of the nanocomposites. - Abstract: Nano-sized boron carbide (B{sub 4}C) and boron nitride (BN) powder were prepared using ball milling. Micro- and milled nano-powders were melt blended with high density polyethylene (HDPE) using a polymer mixer followed by hot pressing to fabricate sheet composites. The tensile and flexural strengths of HDPE nanocomposites were ∼20% higher than their micro counterparts, while those for latter decreased compared to neat HDPE. Thermal neutrons attenuation of the prepared HDPE nanocomposites was evaluated using a monochromatic ∼0.025 eV neutron beam. Thermal neutron attenuation of the HDPE nanocomposites was greatly enhanced compared to their micro counterparts at the same B-10 areal densities. Monte Carlo n-Particles (MCNP) simulations based on the lattice structure modeling also shows the similar filler size dependent thermal neutron absorption.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  16. Safety and immunogenicity of a live attenuated mumps vaccine

    Science.gov (United States)

    Liang, Yan; Ma, Jingchen; Li, Changgui; Chen, Yuguo; Liu, Longding; Liao, Yun; Zhang, Ying; Jiang, Li; Wang, Xuan-Yi; Che, Yanchun; Deng, Wei; Li, Hong; Cui, Xiaoyu; Ma, Na; Ding, Dong; Xie, Zhongping; Cui, Pingfang; Ji, Qiuyan; Wang, Jingjing; Zhao, Yuliang; Wang, Junzhi; Li, Qihan

    2014-01-01

    Background: Mumps, a communicable, acute and previously well-controlled disease, has had recent and occasional resurgences in some areas. Methods: A randomized, double-blind, controlled and multistep phase I study of an F-genotype attenuated mumps vaccine produced in human diploid cells was conducted. A total of 300 subjects were enrolled and divided into 4 age groups: 16–60 years, 5–16 years, 2–5 years and 8–24 months. The groups were immunized with one injection per subject. Three different doses of the F-genotype attenuated mumps vaccine, A (3.5 ± 0.25 logCCID50), B (4.25 ± 0.25 logCCID50) and C (5.0 ± 0.25 logCCID50), as well as a placebo control and a positive control of a licensed A-genotype vaccine (S79 strain) were used. The safety and immunogenicity of this vaccine were compared with those of the controls. Results: The safety evaluation suggested that mild adverse reactions were observed in all groups. No serious adverse event (SAE) was reported throughout the trial. The immunogenicity test showed a similar seroconversion rate of the neutralizing and ELISA antibody in the 2- to 5-year-old and 8- to 24-month-old groups compared with the seroconversion rate in the positive control. The GMT of the neutralizing anti-F-genotype virus antibodies in the vaccine groups was slightly higher than that in the positive control group. Conclusions: The F-genotype attenuated mumps vaccine evaluated in this clinical trial was demonstrated to be safe and have effective immunogenicity vs. control. PMID:24614759

  17. Attenuation of shock waves in copper and stainless steel

    International Nuclear Information System (INIS)

    Harvey, W.B.

    1986-06-01

    By using shock pins, data were gathered on the trajectories of shock waves in stainless steel (SS-304L) and oxygen-free-high-conductivity copper (OFHC-Cu). Shock pressures were generated in these materials by impacting the appropriate target with thin (approx.1.5 mm) flying plates. The flying plates in these experiments were accelerated to high velocities (approx.4 km/s) by high explosives. Six experiments were conducted, three using SS-304L as the target material and three experiments using OFHC-Cu as the target material. Peak shock pressures generated in the steel experiments were approximately 109, 130, and 147 GPa and in the copper experiments, the peak shock pressures were approximately 111, 132, and 143 GPa. In each experiment, an attenuation of the shock wave by a following release wave was clearly observed. An extensive effort using two characteristic codes (described in this work) to theoretically calculate the attenuation of the shock waves was made. The efficacy of several different constitutive equations to successfully model the experiments was studied by comparing the calculated shock trajectories to the experimental data. Based on such comparisons, the conclusion can be drawn that OFHC-Cu enters a melt phase at about 130 GPa on the principal Hugoniot. There was no sign of phase changes in the stainless-steel experiments. In order to match the observed attenuation of the shock waves in the SS-304L experiments, it was necessary to include strength effects in the calculations. It was found that the values for the parameters in the strength equations were dependent on the equation of state used in the modeling of the experiments. 66 refs., 194 figs., 77 tabs

  18. Gentamicin-attenuated Leishmania infantum: a clinicopathological study in dogs.

    Science.gov (United States)

    Daneshvar, Hamid; Molaei, Mohammad M; Afshar, Reza Malekpour; Kamiabi, Hosein; Burchmore, Richard; Hagan, Paul; Phillips, R Stephen

    2009-05-15

    The clinicopathological changes following infection with an attenuated line of Leishmania infantum (L. infantum H-line) were evaluated in mixed breed dogs. Two groups of dogs were infected intravenously (i.v.) or intradermally (i.d.) with L. infantum H-line and two control groups were infected i.v. or i.d. with L. infantum wild-type (L. infantum WT). None of the dogs, which were infected i.v. or i.d. with L. infantum H-line, showed any abnormalities during the observation period. In contrast, two out of three dogs, which were infected i.v. with L. infantum WT, developed clinical signs of disease. In addition, no histopathological changes were seen in the liver and spleen of the dogs infected with the attenuated line of parasite, whereas the histopathological changes in the two dogs infected i.v. with L. infantum WT were severe in form and manifested by infiltration of high numbers of inflammatory cells. No promastigotes were found in cultures set up from spleens and livers of dogs infected with L. infantum H-line at 12 months post-infection, whereas promastigotes were seen in the spleen and liver cultures from 2 dogs infected i.v. with L. infantum WT. Serum levels of total IgG anti-Leishmania antibody were raised in all dogs. The antibody level in the serum of dogs infected i.v. with L. infantum WT was higher than that in dogs infected with L. infantum H-line. These results show no clinicopathological abnormalities in the dogs infected with gentamicin-attenuated L. infantum H-line. Moreover, L. infantum H-line induced IgG anti-Leishmania antibody in the dogs.

  19. Myostatin Attenuation In Vivo Reduces Adiposity, but Activates Adipogenesis.

    Science.gov (United States)

    Li, Naisi; Yang, Qiyuan; Walker, Ryan G; Thompson, Thomas B; Du, Min; Rodgers, Buel D

    2016-01-01

    A potentially novel approach for treating obesity includes attenuating myostatin as this increases muscle mass and decreases fat mass. Notwithstanding, conflicting studies report that myostatin stimulates or inhibits adipogenesis and it is unknown whether reduced adiposity with myostatin attenuation results from changes in fat deposition or adipogenesis. We therefore quantified changes in the stem, transit amplifying and progenitor cell pool in white adipose tissue (WAT) and brown adipose tissue (BAT) using label-retaining wild-type and mstn(-/-) (Jekyll) mice. Muscle mass was larger in Jekyll mice, WAT and BAT mass was smaller and label induction was equal in all tissues from both wild-type and Jekyll mice. The number of label-retaining cells, however, dissipated quicker in WAT and BAT of Jekyll mice and was only 25% and 17%, respectively, of wild-type cell counts 1 month after induction. Adipose cell density was significantly higher in Jekyll mice and increased over time concomitant with label-retaining cell disappearance, which is consistent with enhanced expansion and differentiation of the stem, transit amplifying and progenitor pool. Stromal vascular cells from Jekyll WAT and BAT differentiated into mature adipocytes at a faster rate than wild-type cells and although Jekyll WAT cells also proliferated quicker in vitro, those from BAT did not. Differentiation marker expression in vitro, however, suggests that mstn(-/-) BAT preadipocytes are far more sensitive to the suppressive effects of myostatin. These results suggest that myostatin attenuation stimulates adipogenesis in vivo and that the reduced adiposity in mstn(-/-) animals results from nutrient partitioning away from fat and in support of muscle.

  20. Attenuation of shock waves in copper and stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Harvey, W.B.

    1986-06-01

    By using shock pins, data were gathered on the trajectories of shock waves in stainless steel (SS-304L) and oxygen-free-high-conductivity copper (OFHC-Cu). Shock pressures were generated in these materials by impacting the appropriate target with thin (approx.1.5 mm) flying plates. The flying plates in these experiments were accelerated to high velocities (approx.4 km/s) by high explosives. Six experiments were conducted, three using SS-304L as the target material and three experiments using OFHC-Cu as the target material. Peak shock pressures generated in the steel experiments were approximately 109, 130, and 147 GPa and in the copper experiments, the peak shock pressures were approximately 111, 132, and 143 GPa. In each experiment, an attenuation of the shock wave by a following release wave was clearly observed. An extensive effort using two characteristic codes (described in this work) to theoretically calculate the attenuation of the shock waves was made. The efficacy of several different constitutive equations to successfully model the experiments was studied by comparing the calculated shock trajectories to the experimental data. Based on such comparisons, the conclusion can be drawn that OFHC-Cu enters a melt phase at about 130 GPa on the principal Hugoniot. There was no sign of phase changes in the stainless-steel experiments. In order to match the observed attenuation of the shock waves in the SS-304L experiments, it was necessary to include strength effects in the calculations. It was found that the values for the parameters in the strength equations were dependent on the equation of state used in the modeling of the experiments. 66 refs., 194 figs., 77 tabs.

  1. Intensive Exercise Training During Bed Rest Attenuates Deconditioning

    Science.gov (United States)

    Greenleaf, John E.

    1997-01-01

    Intensive exercise training during bed rest attenuates deconditioning. Med. Sci. Sports Exerc., Vol. 29, No. 2, pp. 207-215, 1997. A 30-d 6 deg head-down bed rest project was conducted to evaluate variable high-intensity, short-duration, isotonic cycle ergometer exercise (ITE) training and high-intensity intermittent resistive isokinetic exercise (IKE) training regimens designed to maintain peak VO2 and muscle mass, strength, and endurance at ambulatory control levels throughout prolonged bed rest. Other elements of the deconditioning (adaptive) syndrome, such as proprioception, psychological performance, hypovolemia, water balance, body composition, and orthostatic tolerance, were also measured. Major findings are summarized in this paper. Compared with response during bed rest of the no exercise (NOE) control group: the ITE training regimen (a) maintained work capacity (peak VO2), (b) maintained plasma and red cell volumes, (c) induced positive body water balance, (d) decreased quality of sleep and mental concentration, and (e) had no effect on the decrease in orthostatic tolerance; the IKE training regimen (f) attenuated the decrease in peak VO2 by 50%, (g) attenuated loss of red cell volume by 40% but had no effect on loss of plasma volume, (b) induced positive body water balance, (i) had no adverse effect on quality of sleep or concentration, and 0) had no effect on the decrease in orthostatic tolerance. These findings suggest that various elements of the deconditioning syndrome can be manipulated by duration and intensity of ITE or IKE training regimens and that several different training protocols will be required to maintain or restore physiological and psychological performance of individuals confined to prolonged bed rest.

  2. Attenuation in the dubbing and subtitling of The Green Mile

    Directory of Open Access Journals (Sweden)

    Lidia Rodríguez

    2015-12-01

    Full Text Available This paper is part of the doctoral thesis entitled “Critique of translation for film dubbing and subtitling from the perspective of discourse analysis. A study applied to "The Green Mile”, written by Ph.D. student Gabriela Saturnina Alanís Uresti, directed by Ph.D. Lidia Rodríguez. It is a qualitative and descriptive study where we contrasted The Green Mile - a 1999 Hollywood film, original in American English - with its translated versions: dubbed and subtitled into Spanish of Mexico. We start from the presupposition that in film translation, some references such as the ones related to sexual behaviors and offensive language are attenuated in order to be strategically polite. Specifically, we analyzed two mechanisms of attenuation: lexical selection whereby a euphemism is used, and discursive modalization. These mechanisms constitute strategies of linguistic, pragmatic and semiotic nature as they appear in original (OV, dubbed (DV and subtitled (SV versions; both in acoustic and visual channels. Therefore, we examine these occurrences on verbal, para-verbal, and non-verbal codes. The theoretical basis includes studies of attenuation, politeness, euphemisms, and linguistic taboos. This paper is based on methodological proposals by Gutiérrez (2008, Nájar (2009, Brown y Levinson (1987, Goffman (1967, Leech (1983, Fraser (1980 Haverkate (1994, Bravo (2001, Albelda (2010, (2005, Albelda y Briz (2010, Briz (2002a; 2002b, Allan y Burridge (2006, Chamizo (2008, Foucault (1987, Seiciuc (2010, Dubois (1969, Dubois et al (1973, and Rodríguez (2004.

  3. Weighted simultaneous algebraic reconstruction technique for tomosynthesis imaging of objects with high-attenuation features

    International Nuclear Information System (INIS)

    Levakhina, Y. M.; Müller, J.; Buzug, T. M.; Duschka, R. L.; Vogt, F.; Barkhausen, J.

    2013-01-01

    Purpose: This paper introduces a nonlinear weighting scheme into the backprojection operation within the simultaneous algebraic reconstruction technique (SART). It is designed for tomosynthesis imaging of objects with high-attenuation features in order to reduce limited angle artifacts. Methods: The algorithm estimates which projections potentially produce artifacts in a voxel. The contribution of those projections into the updating term is reduced. In order to identify those projections automatically, a four-dimensional backprojected space representation is used. Weighting coefficients are calculated based on a dissimilarity measure, evaluated in this space. For each combination of an angular view direction and a voxel position an individual weighting coefficient for the updating term is calculated. Results: The feasibility of the proposed approach is shown based on reconstructions of the following real three-dimensional tomosynthesis datasets: a mammography quality phantom, an apple with metal needles, a dried finger bone in water, and a human hand. Datasets have been acquired with a Siemens Mammomat Inspiration tomosynthesis device and reconstructed using SART with and without suggested weighting. Out-of-focus artifacts are described using line profiles and measured using standard deviation (STD) in the plane and below the plane which contains artifact-causing features. Artifacts distribution in axial direction is measured using an artifact spread function (ASF). The volumes reconstructed with the weighting scheme demonstrate the reduction of out-of-focus artifacts, lower STD (meaning reduction of artifacts), and narrower ASF compared to nonweighted SART reconstruction. It is achieved successfully for different kinds of structures: point-like structures such as phantom features, long structures such as metal needles, and fine structures such as trabecular bone structures. Conclusions: Results indicate the feasibility of the proposed algorithm to reduce typical

  4. Weighted simultaneous algebraic reconstruction technique for tomosynthesis imaging of objects with high-attenuation features

    Energy Technology Data Exchange (ETDEWEB)

    Levakhina, Y. M. [Institute of Medical Engineering, University of Luebeck, Luebeck 23562, Germany and Graduate School for Computing in Medicine and Life Sciences, Luebeck 23562 (Germany); Mueller, J.; Buzug, T. M. [Institute of Medical Engineering, University of Luebeck, Luebeck 23562 (Germany); Duschka, R. L.; Vogt, F.; Barkhausen, J. [Clinic for Radiology, University Clinics Schleswig-Holstein, Luebeck 23562 (Germany)

    2013-03-15

    Purpose: This paper introduces a nonlinear weighting scheme into the backprojection operation within the simultaneous algebraic reconstruction technique (SART). It is designed for tomosynthesis imaging of objects with high-attenuation features in order to reduce limited angle artifacts. Methods: The algorithm estimates which projections potentially produce artifacts in a voxel. The contribution of those projections into the updating term is reduced. In order to identify those projections automatically, a four-dimensional backprojected space representation is used. Weighting coefficients are calculated based on a dissimilarity measure, evaluated in this space. For each combination of an angular view direction and a voxel position an individual weighting coefficient for the updating term is calculated. Results: The feasibility of the proposed approach is shown based on reconstructions of the following real three-dimensional tomosynthesis datasets: a mammography quality phantom, an apple with metal needles, a dried finger bone in water, and a human hand. Datasets have been acquired with a Siemens Mammomat Inspiration tomosynthesis device and reconstructed using SART with and without suggested weighting. Out-of-focus artifacts are described using line profiles and measured using standard deviation (STD) in the plane and below the plane which contains artifact-causing features. Artifacts distribution in axial direction is measured using an artifact spread function (ASF). The volumes reconstructed with the weighting scheme demonstrate the reduction of out-of-focus artifacts, lower STD (meaning reduction of artifacts), and narrower ASF compared to nonweighted SART reconstruction. It is achieved successfully for different kinds of structures: point-like structures such as phantom features, long structures such as metal needles, and fine structures such as trabecular bone structures. Conclusions: Results indicate the feasibility of the proposed algorithm to reduce typical

  5. Estimation of attenuation and moderation by nanostructured materials

    International Nuclear Information System (INIS)

    Artem'ev, V.A.

    2003-01-01

    Peculiarities of the attenuation and slowing down of neutrons in ultradispersed powder with the size of particles ∼ 10 nm are discussed. It is noted that at temperature ∼ 10 K ultradispersed powder possesses the best captured ability of thermal neutrons than ordinary compact material or finely divided powder. Slow neutrons capture is size of ultradispersed particles dependent: captured ability of the material tends to widen with the decrease of particles sizes. Use of ultradispersed powder as moderator is advantageous for the cold neutrons moderation to very cold or for the production of ultracold neutrons [ru

  6. Compact silicon photonic resonance-sssisted variable optical attenuator.

    Science.gov (United States)

    Wang, Xiaoxi; Aguinaldo, Ryan; Lentine, Anthony; DeRose, Christopher; Starbuck, Andrew L; Trotter, Douglas; Pomerene, Andrew; Mookherjea, Shayan

    2016-11-28

    A two-part silicon photonic variable optical attenuator is demonstrated in a compact footprint which can provide a high extinction ratio at wavelengths between 1520 nm and 1620 nm. The device was made by following the conventional p-i-n waveguide section by a high-extinction-ratio second-order microring filter section. The rings provide additional on-off contrast by utilizing a thermal resonance shift, which harvested the heat dissipated by current injection in the p-i-n junction. We derive and discuss a simple thermal-resistance model in explanation of these effects.

  7. Is attenuation correction of myocardial SPET scans worth the effort?

    International Nuclear Information System (INIS)

    Nguyen, D.; Saunders, C.; Dixson, H.; Cook, P.; Burnett, P.; Croll, F.; Dunn, R.; Hasche, E.; Kelleher, P.; Nasser, F.; Wilson, D.; Lee, K.

    1999-01-01

    Full text: In this prospective study, we compared gated (GS), attenuation-corrected (AC) and non-attenuation-corrected (NAC) myocardial SPET scans. 119 consecutive patients were scanned after 800 MBq 99 Tc m -Sestamibi (MIBI) injected at peak stress. AC studies were performed using a Siemens Multispect 3 triple-headed camera with a MμSIC attenuation correction system. Transmission data were provided by an Am241 line source mounted opposite an offset fan beam collimator. Simultaneous emission data were collected from all 3 heads over a 360deg rotation (acquisition time 25 min). The NAC and GS studies were performed using a Siemens ECAM variable-angle dual-headed gamma camera using 8 gating frames over a 90deg rotation (acquisition time 15 min). The myocardium was divided into 9 segments and the studies were reported separately by two observers. Clinical data and angiography results were obtained when available. For GS, myocardial segments with normal systolic wall thickening were considered to have normal perfusion. AC studies were used as the standard for measuring myocardial perfusion. In the 119 patients studied, the overall sensitivity, specificity and accuracy for NAC vs AC were 100%, 25%, 54% and for GS vs AC were 86%, 84% and 85% respectively. There were 265 abnormal segments on NAC. GS demonstrated normal thickening in 90/265 segments and AC demonstrated normal perfusion in 94/265 segments. There were 33 segments with discordant GS and AC. 16/33 segments (9 inferior, 3 anterior, 4 other) with normal thickening had abnormal perfusion on AC and 17/33 segments (9 inferior, 6 anterior, 2 other) with abnormal thickening had normal perfusion on AC. Weight and sex did not predict discordance. In conclusion, attenuation artefacts are common and are not predicted by body habitus or sex. They are usually accurately identified by normal systolic wall thickening on GS. GS is strongly recommended when AC is not available. AC provides additional information, particularly

  8. Seismic attenuation system for the AEI 10 meter Prototype

    International Nuclear Information System (INIS)

    Wanner, A; Bergmann, G; Fricke, T; Lück, H; Mow-Lowry, C M; Strain, K A; Goßler, S; Danzmann, K; Bertolini, A

    2012-01-01

    Isolation from seismic motion is vital for vibration sensitive experiments. The seismic attenuation system (SAS) is a passive mechanical isolation system for optics suspensions. The low natural frequency of a SAS allows seismic isolation starting below 0.2 Hz. The desired isolation at frequencies above a few hertz is 70–80 dB in both horizontal and vertical degrees of freedom. An introduction to the SAS for the AEI 10 m Prototype, an overview of the mechanical design and a description of the major components are given. (paper)

  9. Resilience of chemical industrial areas through attenuation-based security

    International Nuclear Information System (INIS)

    Reniers, G.L.L.; Sörensen, K.; Khan, F.; Amyotte, P.

    2014-01-01

    This paper investigates the possibility of attenuation-based security within chemical industrial areas. Representing chemical industrial areas as mathematical networks, we prove by case-study that the resilience to disaster of such areas may follow a power-law distribution. Furthermore, we examine what happens to the network when highly hazardous installations would be intelligently protected against malicious acts: the network disintegrates into separate smaller networks. Hence, islands are formed with no escalation danger in between. We conclude that it is possible to protect chemical industrial areas in such a way that they are more resilient against terrorism

  10. Multi-resolution inversion algorithm for the attenuated radon transform

    KAUST Repository

    Barbano, Paolo Emilio

    2011-09-01

    We present a FAST implementation of the Inverse Attenuated Radon Transform which incorporates accurate collimator response, as well as artifact rejection due to statistical noise and data corruption. This new reconstruction procedure is performed by combining a memory-efficient implementation of the analytical inversion formula (AIF [1], [2]) with a wavelet-based version of a recently discovered regularization technique [3]. The paper introduces all the main aspects of the new AIF, as well numerical experiments on real and simulated data. Those display a substantial improvement in reconstruction quality when compared to linear or iterative algorithms. © 2011 IEEE.

  11. Natural attenuation of hydrocarbon polluted soils in Mexico

    International Nuclear Information System (INIS)

    Fernandez-Linares, L.; Rojas-Avelizapa, N.; Roldan-Carrillo, T.; Islas-Ramirez, M.

    2009-01-01

    Crude oil and hydrocarbon by-proudcts are the most common pollutants in Mexico. In the last years, the two terms, contamination and remediation have being re-defined; also, based on both the scientific advancement and the human risk, the sustentability of remediation technologies and the definition of cleaning levels has been taking place. In this context, the Natural Attenuation of soils is a viable and low cost remediation choice, defined as the degradation of organic compounds without artificial stimulation, through microbial activity including physical processes, such as volatilization, dilution, sorption, and hydraulic dispersion. (Author)

  12. 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)

  13. Excitations of surface plasmon polaritons by attenuated total reflection, revisited

    International Nuclear Information System (INIS)

    Barchesi, D.; Otto, A.

    2013-01-01

    Many textbooks and review papers are devoted to plasmonics based on a selection of the numerous bibliography. But none describes the details of the first culmination of plasmonics in 1968, when surface plasmons become a field of optics. The coupling of light with the surface plasmon leads to the surface plasmon polariton (SPP). Therefore, the authors chose to associate historical insight (not avoiding a personal touch), a modern mathematical formulation of the excitation of the SPP by attenuated total reflection (ATR), considered as well understood since decades, and experimental applications since 1969, including recent developments.

  14. Electron attenuation anisotropy at crystal surfaces from LEED

    Czech Academy of Sciences Publication Activity Database

    Romanyuk, Olexandr; Bartoš, Igor

    2009-01-01

    Roč. 603, č. 17 (2009), s. 2789-2792 ISSN 0039-6028 R&D Projects: GA ČR GA202/07/0601; GA AV ČR IAA100100628 Institutional research plan: CEZ:AV0Z10100521 Keywords : electron attenuation length, low energy electron diffraction, photoelectron diffraction, electron–solid scattering and transmission, copper * low energy electron diffraction * photoelectron diffraction * electron–solid scattering and transmission * copper Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.798, year: 2009 http://dx.doi.org/10.1016/j.susc.2009.07.024

  15. Attenuation of Electromagnetic Radiation by Haze, Fog, Clouds, and Rain

    Science.gov (United States)

    1975-04-01

    transmission data of Gebbie etal,(3 Gibbons (27) suggests that ai = 0.7 in the wavelength range from 0.61 to 11.48 pim regardless of the meteorological...attenuation at 10 Um becomes 10 to 100 times smaller than at 0.5 jim. It can be also observed that the 8 to 12 pm band is preferable to the 3 to 5 pim ...Water Aerosols and Fog-," Arl. ¢ Ott ., Vol. 9, 1970, pp. 2000-2006. 33. Gebbie, If. A., ot al., "Atmospheric Transmission in the 1 to 14P Region," Pro

  16. Towards Implementing an MR-based PET Attenuation Correction Method for Neurological Studies on the MR-PET Brain Prototype

    Science.gov (United States)

    Catana, Ciprian; van der Kouwe, Andre; Benner, Thomas; Michel, Christian J.; Hamm, Michael; Fenchel, Matthias; Fischl, Bruce; Rosen, Bruce; Schmand, Matthias; Sorensen, A. Gregory

    2013-01-01

    A number of factors have to be considered for implementing an accurate attenuation correction (AC) in a combined MR-PET scanner. In this work, some of these challenges were investigated and an AC method based entirely on the MR data obtained with a single dedicated sequence was developed and used for neurological studies performed with the MR-PET human brain scanner prototype. Methods The focus was on the bone/air segmentation problem, the bone linear attenuation coefficient selection and the RF coil positioning. The impact of these factors on the PET data quantification was studied in simulations and experimental measurements performed on the combined MR-PET scanner. A novel dual-echo ultra-short echo time (DUTE) MR sequence was proposed for head imaging. Simultaneous MR-PET data were acquired and the PET images reconstructed using the proposed MR-DUTE-based AC method were compared with the PET images reconstructed using a CT-based AC. Results Our data suggest that incorrectly accounting for the bone tissue attenuation can lead to large underestimations (>20%) of the radiotracer concentration in the cortex. Assigning a linear attenuation coefficient of 0.143 or 0.151 cm−1 to bone tissue appears to give the best trade-off between bias and variability in the resulting images. Not identifying the internal air cavities introduces large overestimations (>20%) in adjacent structures. Based on these results, the segmented CT AC method was established as the “silver standard” for the segmented MR-based AC method. Particular to an integrated MR-PET scanner, ignoring the RF coil attenuation can cause large underestimations (i.e. up to 50%) in the reconstructed images. Furthermore, the coil location in the PET field of view has to be accurately known. Good quality bone/air segmentation can be performed using the DUTE data. The PET images obtained using the MR-DUTE- and CT-based AC methods compare favorably in most of the brain structures. Conclusion An MR-DUTE-based AC

  17. 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

  18. 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.

  19. Influence of convolution filtering on coronary plaque attenuation values: observations in an ex vivo model of multislice computed tomography coronary angiography

    International Nuclear Information System (INIS)

    Cademartiri, Filippo; Palumbo, Alessandro; La Grutta, Ludovico; Runza, Giuseppe; Maffei, Erica; Mollet, Nico R.; Hamers, Ronald; Bruining, Nico; Bartolotta, Tommaso V.; Midiri, Massimo; Somers, Pamela; Knaapen, Michiel; Verheye, Stefan

    2007-01-01

    Attenuation variability (measured in Hounsfield Units, HU) of human coronary plaques using multislice computed tomography (MSCT) was evaluated in an ex vivo model with increasing convolution kernels. MSCT was performed in seven ex vivo left coronary arteries sunk into oil followingthe instillation of saline (1/∞) and a 1/50 solution of contrast material (400 mgI/ml iomeprol). Scan parameters were: slices/collimation, 16/0.75 mm; rotation time, 375 ms. Four convolution kernels were used: b30f-smooth, b36f-medium smooth, b46f-medium and b60f-sharp. An experienced radiologist scored for the presence of plaques and measured the attenuation in lumen, calcified and noncalcified plaques and the surrounding oil. The results were compared by the ANOVA test and correlated with Pearson's test. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. The mean attenuation values were significantly different between the four filters (p < 0.0001) in each structure with both solutions. After clustering for the filter, all of the noncalcified plaque values (20.8 ± 39.1, 14.2 ± 35.8, 14.0 ± 32.0, 3.2 ± 32.4 HU with saline; 74.7 ± 66.6, 68.2 ± 63.3, 66.3 ± 66.5, 48.5 ± 60.0 HU in contrast solution) were significantly different, with the exception of the pair b36f-b46f, for which a moderate-high correlation was generally found. Improved SNRs and CNRs were achieved by b30f and b46f. The use of different convolution filters significantly modified the attenuation values, while sharper filtering increased the calcified plaque attenuation and reduced the noncalcified plaque attenuation. (orig.)

  20. Modulation of gut microbiota contributes to curcumin-mediated attenuation of hepatic steatosis in rats.

    Science.gov (United States)

    Feng, Wenhuan; Wang, Hongdong; Zhang, Pengzi; Gao, Caixia; Tao, Junxian; Ge, Zhijuan; Zhu, Dalong; Bi, Yan

    2017-07-01

    Structural disruption of gut microbiota contributes to the development of non-alcoholic fatty liver disease (NAFLD) and modulating the gut microbiota represents a novel strategy for NAFLD prevention. Although previous studies have demonstrated that curcumin alleviates hepatic steatosis, its effect on the gut microbiota modulation has not been investigated. Next generation sequencing and multivariate analysis were utilized to evaluate the structural changes of gut microbiota in a NAFLD rat model induced by high fat-diet (HFD) feeding. We found that curcumin attenuated hepatic ectopic fat deposition, improved intestinal barrier integrity, and alleviated metabolic endotoxemia in HFD-fed rats. More importantly, curcumin dramatically shifted the overall structure of the HFD-disrupted gut microbiota toward that of lean rats fed a normal diet and altered the gut microbial composition. The abundances of 110 operational taxonomic units (OTUs) were altered by curcumin. Seventy-six altered OTUs were significantly correlated with one or more hepatic steatosis associated parameters and designated 'functionally relevant phylotypes'. Thirty-six of the 47 functionally relevant OTUs that were positively correlated with hepatic steatosis associated parameters were reduced by curcumin. These results indicate that curcumin alleviates hepatic steatosis in part through stain-specific impacts on hepatic steatosis associated phylotypes of gut microbiota in rats. Compounds with antimicrobial activities should be further investigated as novel adjunctive therapies for NAFLD. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Global seismic attenuation imaging using full-waveform inversion: a comparative assessment of different choices of misfit functionals

    Science.gov (United States)

    Karaoǧlu, Haydar; Romanowicz, Barbara

    2018-02-01

    We present the results of synthetic tests that aim at evaluating the relative performance of three different definitions of misfit functionals in the context of 3-D imaging of shear wave attenuation in the earth's upper mantle at the global scale, using long-period full-waveform data. The synthetic tests are conducted with simple hypothetical upper-mantle models that contain Qμ anomalies centred at different depths and locations, with or without additional seismic velocity anomalies. To build synthetic waveform data sets, we performed simulations of 50 events in the hypothetical (target) models, using the spectral element method, filtered in the period range 60-400 s. The selected events are chosen among 273 events used in the development of radially anisotropic model SEMUCB-WM1 and recorded at 495 stations worldwide. The synthetic Z-component waveforms correspond to paths and time intervals (fundamental mode and overtone Rayleigh waves) that exist in the real waveform data set. The inversions for shear attenuation structure are carried out using a Gauss-Newton optimization scheme in which the gradient and Hessian are computed using normal mode perturbation theory. The three different misfit functionals considered are based on time domain waveform (WF) and waveform envelope (E-WF) differences, as well as spectral amplitude ratios (SA), between observed and predicted waveforms. We evaluate the performance of the three misfit functional definitions in the presence of seismic noise and unresolved S-wave velocity heterogeneity and discuss the relative importance of physical dispersion effects due to 3-D Qμ structure. We observed that the performance of WF is poorer than the other two misfit functionals in recovering attenuation structure, unless anelastic dispersion effects are taken into account in the calculation of partial derivatives. WF also turns out to be more sensitive to seismic noise than E-WF and SA. Overall, SA performs best for attenuation imaging. Our

  2. Theoretical and experimental determination of mass attenuation coefficients of lead-based ceramics and their comparison with simulation

    Directory of Open Access Journals (Sweden)

    Vejdani-Noghreiyan Alireza

    2016-01-01

    Full Text Available Mass attenuation coefficient of lead-based ceramics have been measured by experimental methods and compared with theoretical and Monte Carlo simulation results. Lead-based ceramics were prepared using mixed oxide method and the X-ray diffraction analysis was done to evaluate the crystal structure of the produced handmade ceramics. The experimental results show good agreement with theoretical and simulation results. However at two gamma ray energies, small differences between experimental and theoretical results have been observed. By adding other additives to ceramics and observing the changes in the shielding properties such as flexibility, one can synthesize and optimize ceramics as a neutron shield.

  3. Observation and parametrization of wave attenuation through the MIZ

    Science.gov (United States)

    Ardhuin, F.; Stopa, J.; Dumont, D.; Sévigny, C.; Collard, F.; Boutin, G.

    2016-02-01

    Swell evolution from the open ocean into sea ice is poorly understood, in particular the amplitude attenuation expected from scattering and dissipation. New synthetic aperture radar (SAR) data from Sentinel-1 wave mode reveal intriguing patterns of bright oscillating lines shaped like instant noodles. We investigate cases in which the oscillations are in the azimuth direction, around a straight line in the range direction. This observation is interpreted as the distortion by the SAR processing of crests from a first swell, due to the presence of a second swell. Since deviations from a straight line should be proportional to the orbital velocity towards the satellite, swell height can be estimated. The intensity of the backscatter modulation with a single swell can also be used to retrieve swell height as it is found that the constructive velocity bunching is very sensitive to wave height. Using a novel algorithm to invert the wave directional spectrum, we investigate several cases of attenuation in the Arctic and southern ocean. On this basis we have adjusted an empirical wave-ice dissipation source term in the WAVEWATCH III model.

  4. Mechanical spectroscopy, internal friction and ultrasonic attenuation: Collection of works

    International Nuclear Information System (INIS)

    Magalas, L.B.

    2009-01-01

    An extensive collection of recommended books and proceedings from numerous conferences on internal friction, mechanical spectroscopy, and ultrasonic attenuation is provided. Reflecting the complicated history of the 20th century, books published in English and in Russian are presented in two separate sections. International and national conferences organized in various countries are listed. Supplementary lists referring to conferences held in the People's Republic of China, Poland, Russia, the Soviet Union, and Ukraine are also provided. The interesting evolution of mechanical spectroscopy from internal friction and ultrasonic attenuation in solids is clearly demonstrated, and a choice list of retrospective papers illustrates the evolution of the field. A brief review of mechanical spectroscopy, therefore, is included. Numerous research areas investigated by internal friction and mechanical spectroscopy are addressed, including point defect relaxations, electronic and phonon relaxations, dislocation relaxations, grain boundary relaxations, domain induced relaxations (magnetic, ferroelectric), magnetomechanical relaxations, phase transformations, glass transitions, interface effects as well as a wide array of applications specific to physics and materials science. For many years now, there has been a definite need to provide a thorough list of references that might cover major national conferences and books published in English and other languages. This work strives to achieve this goal.

  5. Tracking the attenuation and nonbreaking dissipation of swells using altimeters

    Science.gov (United States)

    Jiang, Haoyu; Stopa, Justin E.; Wang, He; Husson, Romain; Mouche, Alexis; Chapron, Bertrand; Chen, Ge

    2016-02-01

    A method for systematically tracking swells across oceanic basins is developed by taking advantage of high-quality data from space-borne altimeters and wave model output. The evolution of swells is observed over large distances based on 202 swell events with periods ranging from 12 to 18 s. An empirical attenuation rate of swell energy of about 4 × 10-7 m-1 is estimated using these observations, and the nonbreaking energy dissipation rates of swells far away from their generating areas are also estimated using a point source model. The resulting acceptance range of nonbreaking dissipation rates is -2.5 to 5.0 × 10-7 m-1, which corresponds to a dissipation e-folding scales of at least 2000 km for steep swells, to almost infinite for small-amplitude swells. These resulting rates are consistent with previous studies using in-situ and synthetic aperture radar (SAR) observations. The frequency dispersion and angular spreading effects during swell propagation are discussed by comparing the results with other studies, demonstrating that they are the two dominant processes for swell height attenuation, especially in the near field. The resulting dissipation rates from these observations can be used as a reference for ocean engineering and wave modeling, and for related studies such as air-sea and wind-wave-turbulence interactions.

  6. Natural attenuation of antimony in mine drainage water

    International Nuclear Information System (INIS)

    Manaka, Mitsuo; Yanase, Nobuyuki; Sato, Tsutomu; Fukushi, Keisuke

    2007-01-01

    In this study, we investigated the natural attenuation of antimony (Sb) in the drainage water of an abandoned mine. Drainage water, waste rocks, and ocherous precipitates collected from the mine were investigated in terms of their mineralogy and chemistry. The chemistry of the drainage water was analyzed by measuring pH, oxidation-reduction potential (ORP), and electric conductivity on site as well as by inductively coupled plasma mass spectrometry and ion chromatography. As the drainage flowed downstream, the pH decreased rapidly from 7.05 to 3.26 and then increased slowly to 3.50. In a section where the pH increased, ocherous precipitates occur on a drainage water channel. We determined Sb levels in the drainage water, and the distribution of Sb in the mineral phases of waste rocks and precipitates was estimated by means of a sequential extraction procedure. The results of these investigations indicated that Sb, which is generated by the dissolution of stibnite (Sb 2 S 3 ) and secondary formed Sb minerals in waste rocks, was attenuated by iron-bearing ocherous precipitates, especially schwertmannite, that form over time in the drainage water. The Sb concentrations in the ocherous precipitates were up to 370 mg/kg, whereas the Sb concentrations in the drainage water downstream were below background levels (0.6 μg/L). Bulk distribution coefficients (K d ) for this Sb adsorption to the precipitates ranges up to at least 10 5 L/kg. (author)

  7. R-flurbiprofen attenuates experimental autoimmune encephalomyelitis in mice.

    Science.gov (United States)

    Schmitz, Katja; de Bruin, Natasja; Bishay, Philipp; Männich, Julia; Häussler, Annett; Altmann, Christine; Ferreirós, Nerea; Lötsch, Jörn; Ultsch, Alfred; Parnham, Michael J; Geisslinger, Gerd; Tegeder, Irmgard

    2014-11-01

    R-flurbiprofen is the non-cyclooxygenase inhibiting R-enantiomer of the non-steroidal anti-inflammatory drug flurbiprofen, which was assessed as a remedy for Alzheimer's disease. Because of its anti-inflammatory, endocannabinoid-modulating and antioxidative properties, combined with low toxicity, the present study assessed R-flurbiprofen in experimental autoimmune encephalomyelitis (EAE) models of multiple sclerosis in mice. Oral R-flurbiprofen prevented and attenuated primary progressive EAE in C57BL6/J mice and relapsing-remitting EAE in SJL mice, even if the treatment was initiated on or after the first flare of the disease. R-flurbiprofen reduced immune cell infiltration and microglia activation and inflammation in the spinal cord, brain and optic nerve and attenuated myelin destruction and EAE-evoked hyperalgesia. R-flurbiprofen treatment increased CD4(+)CD25(+)FoxP3(+) regulatory T cells, CTLA4(+) inhibitory T cells and interleukin-10, whereas the EAE-evoked upregulation of pro-inflammatory genes in the spinal cord was strongly reduced. The effects were associated with an increase of plasma and cortical endocannabinoids but decreased spinal prostaglandins, the latter likely due to R to S inversion. The promising results suggest potential efficacy of R-flurbiprofen in human MS, and its low toxicity may justify a clinical trial. © 2014 The Authors. Published under the terms of the CC BY 4.0 license.

  8. Is attenuation correction of myocardial SPECT scans worth the effort?

    International Nuclear Information System (INIS)

    Bui, C.; Nguyen, D.; Dixson, H.; Saunders, C.; Cook, P.; Burnett, P.; Croll, F.; Dunn, R.; Hasche, E.; Kelleher, P.; Nasser, F.; Wilson, D.; Lee, K.

    2000-01-01

    Full text: Gated (GS), attenuation-corrected (AC) and non-attenuation-corrected (NAC) myocardial SPECT scans were performed after injection of 99 Tc m -Sestamibi (MIBI) at peak stress in 253 patients between September 1998 and March 1999. 60 patients have undergone cardiac catheterisation (37 males, 23 females, age range 34-80). For whole heart analysis, significant coronary disease was defined as 50% or greater diameter narrowing in any of the coronary arteries and/or documented myocardial infarction. For vascular territory analysis, significant coronary disease was defined as 50% or greater diameter narrowing of any artery in that territory. The three coronary artery territories were assigned as: left anterior descending (LAD), left circumflex (LCA) and right coronary (RCA). The septum, apex and anterior wall; the lateral wall; and the inferior wall were assigned to the LAD; LCA; and RCA territories respectively. In conclusion for this selected subgroup of patients with angiographic follow-up, NAC, AC and GS were of similar accuracy in the detection of significant CAD in both whole heart analysis and individual vascular territory analysis. AC and GS were of superior specificity when compared with NAC in both whole heart analysis and individual vascular territory analysis. AC and GS may be of additional diagnostic value in improving the specificity of NAC. Further outcome data will be presented. Copyright (2000) The Australian and New Zealand Society of Nuclear Medicine Inc

  9. Mitragynine attenuates withdrawal syndrome in morphine-withdrawn zebrafish.

    Directory of Open Access Journals (Sweden)

    Beng-Siang Khor

    Full Text Available A major obstacle in treating drug addiction is the severity of opiate withdrawal syndrome, which can lead to unwanted relapse. Mitragynine is the major alkaloid compound found in leaves of Mitragyna speciosa, a plant widely used by opiate addicts to mitigate the harshness of drug withdrawal. A series of experiments was conducted to investigate the effect of mitragynine on anxiety behavior, cortisol level and expression of stress pathway related genes in zebrafish undergoing morphine withdrawal phase. Adult zebrafish were subjected to two weeks chronic morphine exposure at 1.5 mg/L, followed by withdrawal for 24 hours prior to tests. Using the novel tank diving tests, we first showed that morphine-withdrawn zebrafish display anxiety-related swimming behaviors such as decreased exploratory behavior and increased erratic movement. Morphine withdrawal also elevated whole-body cortisol levels, which confirms the phenotypic stress-like behaviors. Exposing morphine-withdrawn fish to mitragynine however attenuates majority of the stress-related swimming behaviors and concomitantly lower whole-body cortisol level. Using real-time PCR gene expression analysis, we also showed that mitragynine reduces the mRNA expression of corticotropin releasing factor receptors and prodynorphin in zebrafish brain during morphine withdrawal phase, revealing for the first time a possible link between mitragynine's ability to attenuate anxiety during opiate withdrawal with the stress-related corticotropin pathway.

  10. Natural attenuation of diesel fuel in heavy clay soil

    International Nuclear Information System (INIS)

    Berry, K.A.T.; Burton, D.L.

    1997-01-01

    The application of bioremediation techniques on heavy clay soils contaminated with diesel fuels was studied. Earlier studies suggested that in-situ bioreclamation was only effective on permeable soils such as medium- to coarse-textured sandy or loamy soils. It was assumed that heavy clay soils such as those found in the Red River Valley in Southern Manitoba had physical and chemical properties that would limit the usefulness of natural attenuation. In this study, the disappearance and the natural attenuation of diesel fuel added to soil at a rate of 5000 mg/kg soil in tilled and untilled heavy clay soil was monitored. Three methods of analysis were used: (1) oil and grease content, (2) extractable organics, and (3) the Millipore EnviroGard ELISA method for petroleum hydrocarbons. Effects of the contamination on the soil microbial population were measured using surface CO 2 flux measurements and microbial biomass carbon analysis. Soil moisture contents at all sample times were between 44 and 49 per cent. Soil temperature was also monitored. All three analytical methods used in the study showed the near-complete disappearance of detectable diesel fuel hydrocarbons from the soil after 30 days with half-lives ranging from 11 to 26 days. The advantages and limitations of the ELISA kit were described. No hydrocarbons were detected in the groundwater sample. 45 refs., 7 tabs., 2 figs

  11. 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).

  12. 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.

  13. Temporal Change in Coda Wave Attenuation Observed at Colima Volcano

    Science.gov (United States)

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

    2001-12-01

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

  14. Gamma ray attenuation studies in concrete reinforced with coconut shells

    International Nuclear Information System (INIS)

    Vishnu, C.V.; Joseph, Antony

    2017-01-01

    Gamma ray absorption studies on wood in general is an area of interest. In Kerala, though coconut tree is a common plantation, a systematic study of gamma ray attenuation in coconut shell has not been reported. In the present study, we have made an attempt to carry out such measurements on coconut shells collected from Trichur district. Coconut shells in to the size of 4cm × 4cm was used in these studies and 662 KeV gamma ray counts were measured using 8K channel NaI(Tl) detector. Subsequently we extended these studies by reinforcing concrete with crushed coconut shells, arranged in a layer by layer fashion. Concrete is usually a choice for shielding nuclear radiations. The effect of reinforcing them with coconut shell is also an area of interest. We have carried out absorption studies by using two types of sand also in the concrete mixture. Common sand is not amply available and people use M-sand (Manufactured sand) instead. In the concrete blocks we selectively used common sand and m-sand and its effects on gamma absorption were also investigated. We have estimated both linear and mass attenuation coefficients and the half value layer (HVL) parameter was determined from them. We have noticed an increase in µ/ρ with increase in density of concrete, achieved through the reinforcement. (author)

  15. Mechanical compression attenuates normal human bronchial epithelial wound healing

    Directory of Open Access Journals (Sweden)

    Malavia Nikita

    2009-02-01

    Full Text Available Abstract Background Airway narrowing associated with chronic asthma results in the transmission of injurious compressive forces to the bronchial epithelium and promotes the release of pro-inflammatory mediators and the denudation of the bronchial epithelium. While the individual effects of compression or denudation are well characterized, there is no data to elucidate how these cells respond to the application of mechanical compression in the presence of a compromised epithelial layer. Methods Accordingly, differentiated normal human bronchial epithelial cells were exposed to one of four conditions: 1 unperturbed control cells, 2 single scrape wound only, 3 static compression (6 hours of 30 cmH2O, and 4 6 hours of static compression after a scrape wound. Following treatment, wound closure rate was recorded, media was assayed for mediator content and the cytoskeletal network was fluorescently labeled. Results We found that mechanical compression and scrape injury increase TGF-β2 and endothelin-1 secretion, while EGF content in the media is attenuated with both injury modes. The application of compression after a pre-existing scrape wound augmented these observations, and also decreased PGE2 media content. Compression stimulated depolymerization of the actin cytoskeleton and significantly attenuated wound healing. Closure rate was partially restored with the addition of exogenous PGE2, but not EGF. Conclusion Our results suggest that mechanical compression reduces the capacity of the bronchial epithelium to close wounds, and is, in part, mediated by PGE2 and a compromised cytoskeleton.

  16. Influenza Vaccination Strategies: Comparing Inactivated and Live Attenuated Influenza Vaccines

    Directory of Open Access Journals (Sweden)

    Saranya Sridhar

    2015-04-01

    Full Text Available Influenza is a major respiratory pathogen causing annual outbreaks and occasional pandemics. Influenza vaccination is the major method of prophylaxis. Currently annual influenza vaccination is recommended for groups at high risk of complications from influenza infection such as pregnant women, young children, people with underlying disease and the elderly, along with occupational groups such a healthcare workers and farm workers. There are two main types of vaccines available: the parenteral inactivated influenza vaccine and the intranasal live attenuated influenza vaccine. The inactivated vaccines are licensed from 6 months of age and have been used for more than 50 years with a good safety profile. Inactivated vaccines are standardized according to the presence of the viral major surface glycoprotein hemagglutinin and protection is mediated by the induction of vaccine strain specific antibody responses. In contrast, the live attenuated vaccines are licensed in Europe for children from 2–17 years of age and provide a multifaceted immune response with local and systemic antibody and T cell responses but with no clear correlate of protection. Here we discuss the immunological immune responses elicited by the two vaccines and discuss future work to better define correlates of protection.

  17. Distribution of attenuated goose parvoviruses in Muscovy ducklings.

    Science.gov (United States)

    Takehara, K; Saitoh, M; Kiyono, M; Nakamura, M

    1998-03-01

    With a polymerase chain reaction (PCR) method, goose parvovirus (GPV) DNA was detected in Muscovy ducklings inoculated with attenuated GPV strains, IH and IHC. Strain IH that had been passed 20 times in Muscovy duck embryos could be detected in ducklings at 2- to 28-days after oral inoculation by PCR, however, a cell culture adapted strain IHC that had been passed 15 times in Muscovy duck embryos and then successively 50 times in Muscovy duck embryo fibroblasts could not be detected by 6 days postinoculation by the oral route, but via intramuscular inoculation the virus was detected from 6 dpi. With both strains Muscovy ducklings produced neutralizing antibodies against GPV, but GPV could be recovered from heart muscles even in birds that had high titer of neutralizing antibody. This means that GPV remains in birds for a long period under the presence of high titer of neutralizing antibody in the serum. Recovery of the virus was consistent with PCR results with one exception in which the bird had a neutralizing antibody titer of more than 100,000. After inoculation of these strains, no clinical signs were detected in ducklings. These results suggest that strains IH and IHC can be candidates for live attenuated vaccine for GPV infection.

  18. Skull's acoustic attenuation and dispersion modeling on photoacoustic signal

    Science.gov (United States)

    Mohammadi, Leila; Behnam, Hamid; Tavakkoli, Jahan; Nasiriavanaki, Mohammadreza

    2018-02-01

    Despite the promising results of the recent novel transcranial photoacoustic (PA) brain imaging technology, it has been demonstrated that the presence of the skull severely affects the performance of this imaging modality. We theoretically investigate the effects of acoustic heterogeneity induced by skull on the PA signals generated from single particles, with firstly developing a mathematical model for this phenomenon and then explore experimental validation of the results. The model takes into account the frequency dependent attenuation and dispersion effects occur with wave reflection, refraction and mode conversion at the skull surfaces. Numerical simulations based on the developed model are performed for calculating the propagation of photoacoustic waves through the skull. The results show a strong agreement between simulation and ex-vivo study. The findings are as follow: The thickness of the skull is the most PA signal deteriorating factor that affects both its amplitude (attenuation) and phase (distortion). Also we demonstrated that, when the depth of target region is low and it is comparable to the skull thickness, however, the skull-induced distortion becomes increasingly severe and the reconstructed image would be strongly distorted without correcting these effects. It is anticipated that an accurate quantification and modeling of the skull transmission effects would ultimately allow for aberration correction in transcranial PA brain imaging.

  19. Yiguanjian cataplasm attenuates opioid dependence in a mouse

    Science.gov (United States)

    Gao, Shuai; Gao, Hong; Fan, Yuchen; Zhang, Guanghua; Sun, Fengkai; Zhao, Jing; Li, Feng; Yang, Yang; Wang, Kai

    2016-08-01

    To investigate the effect of Yiguanjian (YGJ) cataplasm on the development of opioid dependence in a mouse model of naloxone-induced opioid withdrawal syndrome. One hundred Swiss albino mice, of equal male to female ratio, were randomly and equally divided into 10 groups. A portion (3 cm2) of the backside hair of the mice was removed 1 day prior to the experiment. Morphine (5 mg/kg) was intraperitoneally administered twice daily for 5 days. YGJ cataplasm was prepared and pasted on the bare region of the mice immediately before morphine administration on day 3 and subsequently removed at the end day 5. On day 6, naloxone (8 mg/kg) was intraperitoneally injected to precipitate opioid withdrawal syndrome. Behavioral observation was performed in two 30-min phases immediately after naloxone injection. The YGJ cataplasm significantly and dose-dependently attenuated morphine-naloxone- induced experimental opioid withdrawal, in terms of withdrawal severity score and the frequencies of jumping, rearing, forepaw licking, and circling behaviors. However, YGJ cataplasm treatment did not alter the acute analgesic effect of morphine. YGJ cataplasm could attenuate opioid dependence and its associated withdrawal symptoms. Therefore, YGJ cataplasm could serve as a potential therapy for opioid addiction in the future.

  20. Dexmedetomidine attenuates the microcirculatory derangements evoked by experimental sepsis.

    Science.gov (United States)

    Miranda, Marcos L; Balarini, Michelle M; Bouskela, Eliete

    2015-03-01

    Dexmedetomidine, an α-2 adrenergic receptor agonist, has already been used in septic patients although few studies have examined its effects on microcirculatory dysfunction, which may play an important role in perpetuating sepsis syndrome. Therefore, the authors have designed a controlled experimental study to characterize the microcirculatory effects of dexmedetomidine in an endotoxemia rodent model that allows in vivo studies of microcirculation. After skinfold chamber implantation, 49 golden Syrian hamsters were randomly allocated in five groups: (1) control animals; (2) nonendotoxemic animals treated with saline; (3) nonendotoxemic animals treated with dexmedetomidine (5.0 μg kg h); (4) endotoxemic (lipopolysaccharide 1.0 mg/kg) animals treated with saline; and (5) endotoxemic animals treated with dexmedetomidine. Intravital microscopy of skinfold chamber preparations allowed quantitative analysis of microvascular variables and venular leukocyte rolling and adhesion. Mean arterial blood pressure, heart rate, arterial blood gases, and lactate concentrations were also documented. Lipopolysaccharide administration increased leukocyte rolling and adhesion and decreased capillary perfusion. Dexmedetomidine significantly attenuated these responses: compared with endotoxemic animals treated with saline, those treated with dexmedetomidine had less leukocyte rolling (11.8 ± 7.2% vs. 24.3 ± 15.0%; P the end of the experiment. Dexmedetomidine decreased lipopolysaccharide-induced leukocyte-endothelial interactions in the hamster skinfold chamber microcirculation. This was accompanied by a significant attenuation of capillary perfusion deficits, suggesting that dexmedetomidine yields beneficial effects on endotoxemic animals' microcirculation.