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  • 1
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A promising approach for the solution of the electrocardiographic inverse problem is the calculation of the cardiac activation sequence from body surface potential (BSP) mapping data. Here, a two-fold regularization scheme is applied in order to stabilize the inverse solution of this intrinsically ill-posed problem. The solution of the inverse problem is defined by the minimum of a non-linear cost function. The L-curve method can be applied for regularization parameter determination. Solving the optimization problem by a Newton-like method, the L-curve may be of pronged shape. Then a numerically unique determination of the optimal regularization parameter will become difficult. This problem can be avoided applying an iterative linearized algorithm. It is shown that activation time imaging due to temporal and spatial regularization is stable with respect to large model errors. Even neglecting cardiac anisotropy in activation time imaging results in an acceptable inverse solution.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillian Magazines Ltd.
    Nature 405 (2000), S. 451-454 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The chromosomal speciation model invokes chromosomal rearrangements as the primary cause of reproductive isolation. In a heterozygous carrier, chromosomes bearing reciprocal translocations mis-segregate at meiosis, resulting in reduced fertility or complete sterility. Thus, chromosomal ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 33 (2003), S. 321-330 
    ISSN: 1434-6036
    Keywords: PACS. 33.35.+r Electron resonance and relaxation – 36.40.-c Atomic and molecular clusters – 75.20.-g Diamagnetism, paramagnetism, and superparamagnetism – 75.75.+a Magnetic properties of nanostructures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The magnetic properties of the cyclic compound [Fe6(bicine)6] LiClO4 . 2MeOH are reported. The cluster Fe6(bicine)6 forms an antiferromagnetically coupled ring structure of Fe III ions. The magnetic susceptibility is measured between 2 and 300 K and yields the exchange coupling of J/k B = - 27.5±0.5 K. The field dependence of the magnetic moment is studied at 3 and 6 K in magnetic fields up to 5 T. The zero-field splitting of the first excited spin states with S = 2 and 3 are determined by ESR at 94 GHz. The intra-molecular interactions of the Fe III ions are analyzed and the on-site anisotropy of the Fe III due to the ligand-configuration is determined to d /k B = - 0.633±0.008K.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 26 (2002), S. 199-209 
    ISSN: 1434-6036
    Keywords: PACS. 76.60.-k Nuclear magnetic resonance and relaxation – 75.20.Hr Local moment in compounds and alloys; Kondo effect, valence fluctuations, heavy fermions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Nuclear magnetic resonance (NMR) and relaxation of 63Cu and 65Cu in a powder sample of the heavy-fermion paramagnet CeCu6 is measured and analysed quantitatively. Five different Cu sites are accessible to a detailed analysis. We derive quadrupolar splitting frequencies, Ce to Cu transferred hyperfine field coupling constants, and transversal as well as longitudinal relaxation behaviour. Only small relaxation anomalies are observed at the orthorhombic to monoclinic structural phase transition of CeCu6. We point to the different importance of transferred hyperfine interaction and local conduction electron density for static or dynamic part, respectively, of Cu hyperfine interaction. The different sign of the transferred hyperfine interaction from Ce3+ to different Cu neighbours reveals the different competing interaction mechanisms, giving rise to the heavy-fermion paramagnetic behavior of CeCu6.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 15 (2000), S. 21-27 
    ISSN: 1434-6036
    Keywords: PACS. 76.60.Cq Chemical and Knight shifts - 71.20.-b Electron density of states and band structure of crystalline solids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: High-resolution 13C nuclear magnetic resonance with 1H cross polarization and 1H decoupling under magic angle spinning is measured for the quasi-one dimensional organic conductor diperylene hexafluorophosphate (including tetrahydrofurane solvent molecules) at temperatures between 160 K and 270 K. Ab initio molecular orbital calculations are used for chemical shift analysis and for assignment of Knight shifted lines and individual carbon positions. The coexistence of neutral perylene molecules and perylene radicals in the same radical cation salt is revealed. From Knight and chemical shifts we were able to distinguish two inequivalent perylene radicals within the conducting stack. The spin density distribution of the molecular electronic wave function is determined quantitatively for these radicals.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0584
    Keywords: Key words Neonatal alloimmune thrombocytopenia ; Platelet α2β1-integrin ; Polymorphisms ; Platelet antigens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Alloimmunization against human platelet antigen (HPA)-5 may lead to neonatal alloimmune thrombocytopenia. The HPA-5 dimorphism is expressed on the platelet α2β1 integrin. The density of this receptor is associated with another dimorphism of the α2β1 integrin (nucleotide-807C/T). We hypothesized that anti-HPA-5b-induced neonatal thrombocytopenia is more likely to occur if the receptor is expressed at high than at low levels. Among 933 mother–child pairs, we identified 79 HPA-5aa mothers giving birth to a HPA-5ab offspring. Seventeen mothers had HPA-5b antibodies, but the offspring had a normal platelet count. We genotyped the offspring and mothers for the α2-807C/T dimorphism to evaluate its relationship to antibody formation. There was no difference between the frequency of the 807C/T dimorphism among children delivered from alloimmunized mothers and those from mothers without antibodies (P〉0.3). The frequency of the 807C/T dimorphism was not different in the two maternal groups. In three maternal–fetal incompatibilities, we observed at delivery normal platelet counts of platelets typed HPA-5b-α2807T, despite increasing maternal antibody titers during the pregnancy. Our data do not support the hypothesis that the 807C/T dimorphism in the HPA-5ab children is a predisposing factor to either elicit alloimmunization against HPA-5b or for neonatal alloimmune thrombocytopenia.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-0584
    Keywords: Key words Acute myelogenous leukemia ; Stem-cell transplantation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Between February 1982 and 1999, 118 consecutive patients (65 male, 53 female) with acute myelogenous leukemia (AML), with a median age of 35 years (range 17–56 years), received stem-cell grafts from a human leukocyte antigen-identical sibling (n=71), one-antigen-mismatched family member (n=2), matched unrelated donor (n=15), one-antigen-mismatched unrelated donor (n=4) or an autologous (n=26) graft. At the time of transplant, 56 patients were in the first complete remission (CR), 27 in the second CR, 6 in untreated relapse, 17 in primary refractory, and 12 in refractory relapse. The French-American-British classification (FAB) subtypes were as follows: M1 (n=25), M2 (n=28), M3 (n=11), M4 (n=32), M5 (n=16), M6 (n=6). For conditioning, most patients underwent total body irradiation-containing regimens. As of 28 February, 1999, probability of leukemia-free survival (LFS) is 58% for patients after related and 45% after unrelated stem-cell transplantation (SCT). The probability of LFS is 70% for patients given allogeneic transplants in the first CR compared with 33% for those beyond the first CR at SCT. In autologous stem-cell graft recipients, the probability of LFS is 37%. Transplant-related mortality was 28% after related, 20% after unrelated, and 4% after autologous SCT. Probability of relapse for patients given related-donor stem-cell grafts in the first CR and beyond the first CR is 30% and 67%, 55% after unrelated and 63% after autologous stem-cell grafting. Thus, myeloablative therapy followed by allogeneic stem-cell infusion has a high curative potential for patients with AML in remission and offers substantial benefits to patients in advanced disease.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Annals of biomedical engineering 28 (2000), S. 1229-1243 
    ISSN: 1573-9686
    Keywords: Electrocardiography ; Forward problem ; Magnetocardiography ; Vortex sources
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract A hybrid boundary element method (BEM)/finite element method (FEM) approach is proposed in order to properly consider the anisotropic properties of the cardiac muscle in the magneto- and electrocardiographic forward problem. Within the anisotropic myocardium a bidomain model based FEM formulation is applied. In the surrounding isotropic volume conductor the BEM is adopted. Coupling is enabled by requesting continuity of the electric potential and the normal of the current density across the boundary of the heart. Here, the BEM part is coupled as an equivalent finite element to the finite element stiffness matrix, thus preserving in part its sparse property. First, continuous convergence of the coupling scheme is shown for a spherical model comparing the computed results to an analytic reference solution. Then, the method is extended to the depolarization phase in a fibrous model of a dog ventricle. A precomputed activation sequence obtained using a fine mesh of the heart was downsampled and used to calculate body surface potentials and extracorporal magnetic fields considering the anisotropic bidomain conductivities. Results are compared to those obtained by neglecting in part or totally (oblique or uniform dipole layer model) anisotropic properties. The relatively large errors computed indicate that the cardiac muscle is one of the major torso inhomogeneities. © 2000 Biomedical Engineering Society. PAC00: 8719Nn, 8719Hh, 8719Ff, 8710+e, 8717Nn
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