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  • 1
    ISSN: 1432-1084
    Keywords: Digital radiography ; Image processing ; Subtraction ; Thorax ; Tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Digital tomosynthesis makes it possible to reconstruct multiple tomographs from digital data obtained during a single tomographic motion and permits digital processing, which adds a number of special advantages to the well-known advantages of conventional tomography. We performed digital tomosynthesis with a fluororadiographic TV unit with tomographic function which was capable of producing pulsed low-and high-energy X-rays alternately, and we studied digital image processing to improve the image clarity of the reconstructed tomographs. To identify the optimal parameters for processing image data by means of spatial frequency filtration we evaluated the spatial frequency distribution of image data in linear tomographs of the lung, and on the basis of the results of this study we developed several types of digital image processing to reduce tomographic blur and system noise, to improve visualisation of faint opacities, to reduce resistant tomographic blur as well as overall blur, and to generate low-noise bone images based on dual-energy subtraction tomosynthesis.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1750
    Keywords: Key words:Mycobacterium avium-intracellulare—Chest HRCT findings—Chronic sinusitis—Bronchiectasis—Bronchoalveolar lavage fluid.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. We tried to characterize the clinical features and findings on chest high resolution computed tomography (HRCT) of patients with Mycobacterium avium-intracellulare (MAI) pulmonary infection without known predisposing lung disease and with no immunodeficiency. We also aimed to clarify the small airway and alveolar inflammation using bronchoalveolar lavage (BAL) from the affected regions. MAI infection was diagnosed in 53 patients from respiratory samples, including sputum and materials obtained using a fiberoptic bronchoscope. None had a predisposing lung disease or immunodeficiency, as assessed by medical history, routine laboratory data, and previously normal chest radiographs and/or CT scans. The mean age of the 53 patients was 60 ± 11 years, and 48 were nonsmoking females. They had few respiratory symptoms, although 42% had chronic paranasal sinusitis. Chest HRCT findings showed centrilobular small nodules and ectasia of small bronchi and/or bronchioles located mainly in segment (S) 2, 3, 4, and 5. S1, which is usually affected by pulmonary tuberculosis, was completely free of these opacities. The BAL study revealed that the predominant cells were activated T lymphocytes and neutrophils. The CD4+/CD8+ ratio increased significantly. Bacteriology was negative for other bacteria and fungi. Although our patients did not present with distinct respiratory symptoms, the regions affected by MAI showed a chronic inflammation of mainly neutrophils and activated T lymphocytes. The presence of chronic sinusitis may be merely coincidental. However, its high prevalence and the finding of bronchiectasis in chest HRCT raise the question of whether silent bronchiectasis may be a predisposition.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 110 (1998), S. 339-344 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We study a Hamiltonian of S = 1/2 spins with two-, three and four-spin exchange interactions on the triangular lattice as a possible model of the nuclear magnetism of solid 3 He layers. The spin wave theory shows that the “tetrahedral” ground state, which was shown to be favoured by the four-spin exchange interaction in our previous paper, is stable against quantum fluctuations in some parameter region. Since this state has a scalar chiral long-range order, a phase transition occurs at a finite temperature even though the Hamiltonian has a full rotational symmetry in the spin space. Critical behavior of this phase transition was examined by classical Monte Carlo simulations. The specific heat diverges much more strongly than that of the 2D Ising model.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 111 (1998), S. 583-588 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We study quantum effects in a system of S = 1/2 spins with two–, three and four–spin exchange interactions on the triangular lattice, a possible model of the nuclear magnetism of solid 3 He layers. The ground state phases found in our previous work are studied by using the linear spin–wave theory. The “uuud” state shows a very flat spin–wave dispersion, which suggests that this state, though locally stable, will not survive non–linear quantum effects. The “tetrahedral” state, which has long–range order of a scalar chirality, is found to be stable against spin wave fluctuations. The ground state energies of different phases are compared. Results of numerical analysis of finite size clusters are also presented.
    Type of Medium: Electronic Resource
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