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  • 1995-1999  (8)
  • 1
    ISSN: 1432-1084
    Keywords: Key words. Lung ; Lung nodule ; Lung neoplasms ; High-resolution CT
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The aim of this study was to analyze different characteristics on high-resolution computed tomography (HRCT) that help differentiate benign solitary pulmonary lesions (BSPLs) from malignant solitary pulmonary lesions (MSPLs). High-resolution computed tomography was performed on 104 consecutive patients with SPLs. The whole lesion was examined with a slice thickness of 1 mm and a 12-cm field of view. All lesions were surgically excised within 24 h of the CT examination. Satellite nodules, cavitations, and necrosis were found only in MSPLs. Useful characteristics for the differentiation of BSPLs from MSPLs were the presence of spicules (p 〈 0.00005), spicules extending to the visceral pleura (p 〈 0.0005), the vessel sign (p 〈 0.0005), pleural retraction (p 〈 0.001), circumscribed pleural thickening (p 〈 0.001), the bronchus sign (p 〈 0.005), the presence of ground-glass attenuation adjacent to the SPL (p 〈 0.01), the density of the lesion (p 〈 0.05), and the length of spicules (p 〈 0.05). Using the significant characteristics p 〈 0.01 for the identification of MSPLs, a sensitivity of 91.4 % and a specificity of 56.5 % (accuracy of 83.7 %) was found. A precise morphological assessment of the periphery of the pulmonary lesion is necessary. The HRCT technique is useful in differentiation of BSPLs from MSPLs. However, metastases strongly resembled benign lesions in terms of size and edge type, and chronic inflammatory pseudotumors as a group mimic MSPLs.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 117 (1999), S. 945-949 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The linear compressibilities and the thermal expansion of an untwinned, nearly optimal doped YBa 2 Cu 3 O 6.94 single crystal were measured along the three crystallographic axes with a high-resolution dilatometer mounted in a high-pressure cell. The measurements were performed in a temperature range from 50 K to 320K under hydrostatic gas pressure of maximal 0.65 GPa. At a temperature of 300 K the measured bulk modulus is reduced and shows a very strong enhancement under increasing pressure due to pressure-induced oxygen ordering. This ordering process can also be related to a glass transition seen in the thermal expansion above 225 K. At lower temperatures, when oxygen ordering is frozen, the bulk modulus is increased and shows a significantly reduced enhancement under pressure. This pressure dependence, however, is still anomalous high, probably caused by bonds of extremely different compressibilities within the unit cell. The widely spread literature data of the bulk modulus can be explained by this high pressure dependence.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 117 (1999), S. 1013-1017 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present results of reflectivity measurements with E∥candE ⊥ c on NdBa 2 Cu 3 O x (Nd123) single crystals close to full oxygen doping. Along the c–axis the optical conductivity $$\sigma _1^c $$ shows a well developed absorption band around 450 cm −1 at all temperatures. The in–plane optical properties are dominated by crystal–field excitations at low energies, a prominent step at 400 cm −1 and a weaker feature between 500 - 550 cm −1. A comparison of $$\sigma _1^c $$ and the in–plane scattering rate Γab (ω) with neutron scattering derived spin susceptibility spectra suggests that the in–plane and out–of–plane anomalies are caused by the same mechanism, probably electron–spin scattering.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-7357
    Keywords: 74.25.Bt ; 74.25.Fy ; 74.62.Dk ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Measurements of the anisotropic electrical resistivity, the Hall Effect, and the specific heat anomaly at Tc of Ca-doped YBa2Cu3Ox single crystals of various Ca and O contents are presented. The transport properties are discussed in terms of charge and spin separated quasiparticles and confirm that by doping Ca onto Y sites the hole concentration, nh, can be extended beyond the value achieved with O-doping alone at x=7.0. The jump in the specific heat at Tc which increases monotonously with x up to x=7.0 in Ca-free crystals displays a maximum in highly oxygenated Ca-doped crystals. This maximum, however, is displaced from the Tc(nh) maximum to higher values of nh, consistent with the model of induced superconductivity in the CuO chains.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Former pressure experiments on YBa2Cu3Ox single crystals showed only small dTc/dp values at high oxygen contents (6.9≤x≤7.0), which corresponds to an almost optimal hole-doping nh. By Ca-doping these investigations can be extended to the heavily overdoped region. Reducing then the oxygen content allows to return to the optimal hole concentration nh,opp which gives the maximum transition temperature Tc,max for this Ca-content. Oxygen and Ca-doping of YBa2Cu3Ox single crystals are used to determine the parabolic Tc(nh) dependency by ac-susceptibility measurements under hydrostatic pressure conditions up to 0.6 GPa. In order to avoid pressure induced oxygen ordering processes the samples were held below 100 K during the experiment including all pressure changes. The Ca-doped highly oxygenated single crystals show large negative dTc/dp values. Reducing the oxygen content increases dTc/dp to zero, as expected. A further reduction of the oxygen content increases the dTc/dp values much faster than expected from the overdoped region. These findings are interpreted to arise from the anisotropic pressure effect on Tc with a pressure effect in c-axis direction that is mainly due to hole doping and with additional structural effects when pressure is applied in a- and b-axis direction.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 117 (1999), S. 951-955 
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The specific heat of Nd(Y)Ba 2 Cu 3 O x single crystals without substitution of Nd for Ba has been measured for various oxygen contents. In comparison with YBa 2 Cu 3 O x , the maximum attainable transition temperature of the crystals is about 4 K higher and shifted from x = 6.92 to x = 7.0, the highest possible oxygen content. In spite of the difference in the T c (x) dependences, the jump in the specific heat ΔC/T c at T c in both systems increases continuously being maximum at x = 7.0. Bond valence sum calculations based on neutron diffraction data point to a retarded generation of holes with increasing oxygen content in the Nd system and a different hole distribution between the chains and the planes in comparison to YBa 2 Cu 3 O x accounting for the different behaviour of both systems.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Westudied T c of Y Ba 2 Cu 3 O x (Y123), Y 0.89 Ca 0.11 Ba 2 Cu 3 O x (YCa123) and NdBa 2 Cu 3 O x (Nd123) single crystals with various oxygen contents x. Compared to T c (x) of Y123 the T c (x) curves of YCa123 are shifted to lower oxygen contents and the maximum transition temperature T c,max decreases with increasing Ca content whereas in Nd123 T c (x) is shifted to higher oxygen contents and T c,max is increased. According to the universal parabolic T c (n h ) behavior the differences in T c (x) of Y123, YCa123 and Nd123 can be ascribed to different hole concentrations n h in the CuO 2 planes caused by doping via changes in chemistry or structure. In order to study the influence of structural changes on T c we examined the hydrostatic pressure effect dT c /dp (p ≤0.6GPa). In the underdoped region, at n h ≈0.11, the examined compounds show a peak in dT c /dp which is very pronounced for systems with well ordered CuO chains. As this peak occurs at the same n h in all investigated systems it is not caused by oxygen ordering, but its origins might be found in a strong influence of lattice deformations on the electronic structure.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Singly charged gold cluster ions from a laser-vaporization source are transferred into a Penning trap and subjected to electron bombardment. The charged reaction products are analyzed by time-of-flight mass spectrometry after axial ejection from the trap. They include singly charged cluster fragments, multiply charged clusters of the initial size and multiply charged cluster fragments. The multiply charged clusters are selected and further investigated by collision induced dissociation. Two types of reactions can be distinguished: Dissociation into several charged fragments and evaporation of neutrals. Several features of multiply charged clusters relevant for future investigations are reviewed.
    Type of Medium: Electronic Resource
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