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Träfflista för sökning "WFRF:(Markenroth Bloch Karin) "

Sökning: WFRF:(Markenroth Bloch Karin)

  • Resultat 1-10 av 61
  • [1]234567Nästa
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1.
  • Rolf, Marijn P, et al. (författare)
  • Sequence optimization to reduce velocity offsets in cardiovascular magnetic resonance volume flow quantification - A multi-vendor study
  • 2011
  • Ingår i: JOURNAL OF CARDIOVASCULAR MAGNETIC RESONANCE. - : Taylor and Francis / BioMed Central. - 1097-6647. ; 13
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: Eddy current induced velocity offsets are of concern for accuracy in cardiovascular magnetic resonance (CMR) volume flow quantification. However, currently known theoretical aspects of eddy current behavior have not led to effective guidelines for the optimization of flow quantification sequences. This study is aimed at identifying correlations between protocol parameters and the resulting velocity error in clinical CMR flow measurements in a multi-vendor study. Methods: Nine 1.5T scanners of three different types/vendors were studied. Measurements were performed on a large stationary phantom. Starting from a clinical breath-hold flow protocol, several protocol parameters were varied. Acquisitions were made in three clinically relevant orientations. Additionally, a time delay between the bipolar gradient and read-out, asymmetric versus symmetric velocity encoding, and gradient amplitude and slew rate were studied in adapted sequences as exploratory measurements beyond the protocol. Image analysis determined the worst-case offset for a typical great-vessel flow measurement. Results: The results showed a great variation in offset behavior among scanners (standard deviation among samples of 0.3, 0.4, and 0.9 cm/s for the three different scanner types), even for small changes in the protocol. Considering the absolute values, none of the tested protocol settings consistently reduced the velocity offsets below the critical level of 0.6 cm/s neither for all three orientations nor for all three scanner types. Using multilevel linear model analysis, oblique aortic and pulmonary slices showed systematic higher offsets than the transverse aortic slices (oblique aortic 0.6 cm/s, and pulmonary 1.8 cm/s higher than transverse aortic). The exploratory measurements beyond the protocol yielded some new leads for further sequence development towards reduction of velocity offsets; however those protocols were not always compatible with the time-constraints of breath-hold imaging and flow-related artefacts. Conclusions: This study showed that with current systems there was no generic protocol which resulted into acceptable flow offset values. Protocol optimization would have to be performed on a per scanner and per protocol basis. Proper optimization might make accurate (transverse) aortic flow quantification possible for most scanners. Pulmonary flow quantification would still need further (offline) correction.
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2.
  • Chulkov, L. V., et al. (författare)
  • Three-body correlations in electromagnetic dissociation of Borromean nuclei: The He-6 case
  • 2005
  • Ingår i: Nuclear Physics A. - : Elsevier. - 0375-9474. ; 759:1-2, s. 23-42
  • Tidskriftsartikel (refereegranskat)abstract
    • Dissociation of He-6 on a lead target has been studied at 240 MeV/u. The four-momenta of the two neutrons in coincidence with alpha-particles have been measured and used to reconstruct the three-body energy and angular correlations in the final state. For the first time, three-body correlations were included in the analysis of the He-6 dissociation data, and compared with calculations assuming a dipole mode for the electromagnetic dissociation. In addition, the experimental data have been analyzed using a series expansion of the final transition amplitude into hyperspherical functions, showing the importance of both nn and alpha n final-state interactions. It is shown that the dissociation process is governed by a transition of one neutron from the p-shell in the 6He ground state to the s-shell in the continuum further indicating that the role of the transition through an intermediate He-5(3/2(-)) state is more important than expected. (c) 2005 Elsevier B.V. All rights reserved.
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3.
  • Cortina-Gil, D., et al. (författare)
  • Nuclear and Coulomb breakup of 8B
  • 2003
  • Ingår i: Nucl. Phys. A. - : Elsevier. ; 720:1-2, s. 3-19
  • Tidskriftsartikel (refereegranskat)
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4.
  • Cortina-Gil, D., et al. (författare)
  • One-neutron knockout of O-23
  • 2005
  • Ingår i: European Physical Journal A. - : Springer. - 1434-601X .- 1434-6001. ; 25, s. 343-346
  • Konferensbidrag (refereegranskat)abstract
    • Breakup reactions were used to study the ground-state configuration of the neutron-rich isotope O-23. The O-22 fragments produced in one-nucleon removal from O-23 at 938 MeV/nucleon in a carbon target were detected in coincidence with de-exciting gamma rays, allowing to discern between 220 ground-state and excited-states contributions. From the comparison of exclusive experimental momentum distributions for the one-neutron removal channel to theoretical momentum distributions calculated in an Eikonal model for the knockout process, and spin and parity assignment of I-pi = 1/2(+) was deduced for the 230 ground state. This result solved the existent experimental discrepancy.
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7.
  • Axelsson, L., et al. (författare)
  • Study of the unbound nucleus 11N by elastic resonance scattering
  • 1996
  • Ingår i: Physical Review C (Nuclear Physics). - : American Physical Society. - 0556-2813. ; 54:4, s. 1511-1514
  • Tidskriftsartikel (refereegranskat)abstract
    • Resonances in the unbound nucleus 11N have been studied, using the resonance scattering reaction 10C+p. The data give evidence for three states above the 10C+p threshold with energies 1.30, 2.04, and 3.72 MeV. These states can be interpreted, in a potential-model analysis, as the ground state and the first two excited states with spin-parity 1 / 2+, 1 / 2-, and 5 / 2+ arising from the shell-model orbitals 1s1 / 2, 0p1 / 2, and 0d5 / 2. A narrow state superposed on a broad structure found at higher energy could be interpreted as the mirror state of the 3 / 2- in 11Be shifted down in energy. This shift would suggest a large radius of the potential.
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8.
  • Bergmann, U.C., et al. (författare)
  • Light exotic isotopes: recent beam developments and physics applications at ISOLDE
  • 2002
  • Ingår i: Nuclear Physics, Section A. - : Elsevier. - 0375-9474. ; 701:1-4, s. 363-368
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper is divided in three parts: (i) the measurement of yields and decay losses of Li and Be isotopes released from a thin foil tantalum target at the CERN/ISOLDE PS-Booster; (ii) results from β-decay experiments on 12Be and 14Be, an improved half-life of 21.49(3) ms has been obtained for 12Be; (iii) the β-decay of 9C. An outline of the analysis procedure to determine the branching at high excitation energies is given. The ground-state branch has been determined to 54.1(15)%.
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9.
  • Bergmann, U C, et al. (författare)
  • New information on b-delayed neutron emission from 12,14Be
  • 1999
  • Ingår i: Nuclear Physics, Section A. - : Elsevier. - 0375-9474. ; 658:2, s. 129-145
  • Tidskriftsartikel (refereegranskat)abstract
    • The β-delayed neutron branches from neutron-rich Be-isotopes have been measured with a setup sensitive down to thermal energies. For 14Be a new value of Pn = 101 ± 4% has been found for the total neutron-emission probability and an upper limit of 2.4% (95% confidence level) is imposed on the combination P2n + 3P3n of multi-neutron emission probabilities. Moreover, an improved value of Pn = 0.50 ± 0.03% has been obtained for 12Be. A time-correlation method, previously developed for a continuous radioactive beam to determine neutron branching ratios, has been revised and adapted to the pulsed secondary beam at ISOLDE, CERN.
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10.
  • Bergmann, U.C., et al. (författare)
  • On the b-decay of 9C
  • 2001
  • Ingår i: Nuclear Physics A. - : Elsevier. ; 692:3-4, s. 427-450
  • Tidskriftsartikel (refereegranskat)abstract
    • In β-decay experiments on 9C at CERN/ISOLDE the β-strength was determined to the ground state, the 12.2 MeV excited state and the Isobaric Analog State (IAS) at 14.655 MeV in 9B. A large β-strength asymmetry is deduced for the mirror transitions of 9C and 9Li to states around 12 MeV excitation energy. A satisfactory description of the three-body decay from a narrow energy region around the 12.2 MeV resonance is obtained within a sequential model involving the ground and first-excited states of 5Li and 8Be. From the study of angular correlations the spin of the 12.2 MeV state is determined as 5/2−. For the first time the population of the IAS is observed in β-decay and new information on the decay of this state is obtained. The advantages of a closely packed, highly segmented detector setup are demonstrated.
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  • Resultat 1-10 av 61
  • [1]234567Nästa
 
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